climate fact sheets pirc

7/31/2019 Climate Fact Sheets PIRC

1/27

climate factsheets

www.pirc.info/factsheets
http://www.pirc.info/factsheetshttp://www.pirc.info/factsheets


2/27

Climate change research encompasses tens of

thousands of peer-reviewed studies, decades

of observations and the work of thousands of

scientists. But too often this valu able know-

ledge doesnt reach the people who need it most:climate change communicators & campaigners.

This document takes the latest scientific research

and translates it into practical factsheets on a

wide range of climate change topics, ensuring

that those responsible for communicating it

to a wider public have easy access to the best

available evidence.

welcomeYou cant fake spring coming earlier, or trees grow-

ing higher up on mountains, or glaciers retreating

for kilometres up valleys, or shrinking ice cover in

the Arctic, or birds changing their migration times,

or permafrost melting in Alaska, or the tropics ex-panding, or ice shelves on the Antarctic peninsula

breaking up, or peak river flow occurring earlier in

summer because of earlier snowmelt, or sea level

rising faster and faster, or any of the thousands of

similar examples. ... put all the data from around

the world together, and you have overwhelming

evidence of a long-term warming trend.

- m l Pg

New Scientist

4th December 2009wrn byAlice Hooker-Stroud, Josie Wexler, Richard Hawkins,Guy Shrubsole and Tim Holmes.

Dgnd byStephen Wildish and Richard Hawkins.

First published in the United Kingdom 2012 by PIRC.

Public Interest Research Centre is a company limited by guarantee.Registered Charity No.: 266446. Registered No.: 1112242.Registered Office: Y Plas, Machynlleth, Wales, SY20 8ER.

The Climate Factsheets are licensed under a Creative CommonsAttribution-ShareAlike 3.0 Unported License. We actively encouragereproduction in all forms and by all means.

crv cn, 2012 PiRc

Printed on 100% recycled, FSC paper using vegetable-based inks.

isBN: 978-0-9503648-5-8
http://www.stephenwildish.co.uk/http://www.stephenwildish.co.uk/


3/27

PIRC is an independent charity integrating research

on climate change, energy & economics - widening

its audience and increasing its impact. We sit between

research organisations and decision-makers;

translating technical research into engaging material

which inspires lasting change.

Since the failure of the Copenhagen climate talks

in 2009 and the Climategate debacle of early 2010,

media interest in climate science has declined, and

the public become somewhat more sceptical about its

veracity. Yet the evidence base itself has only become

more robust in that time. Conveying the certainties and

uncertainties of climate science to the public - through

a media that has become much more polarised about

the subject - i s a recurrent challenge for campaigners.

Responding to this, PIRC has put together the following

set of factsheets, covering different aspects of climate

science. The factsheets look at the evidence for

climate change from a range of angles, such as global

temperature trends and Arctic ice melt, and traces the

fingerprint of climate change in various phenomena,

from floods and heatwaves to wildfires and species

extinctions. Each briefing contextualises the issue in

question, summarises the background science, and

addresses common objections raised by sceptics.

Drawing on the latest peer-reviewed studies, they are

intended to be a solid, reliable and concise guide for

campaigners wishing to communicate climate science

with accuracy and confidence.

aBoUt PiRc coNteNts

10 aRctic sea ice

06 thaNKss

07 foRewoRD

28 RefeReNces

08 temPeRatURe

14 el Nio12 DRoUGht

18 heatwaVes

20 sNow & colD 22 sPecies eXtiNctioN

16 flooDiNG

24 the seasoNs 26 wilDfiRes

The Arctic contains a thin, vulnerable layer of sea ice whichreaches a minimum every September, providing a regularopportunity to highlight the impacts of climate change.

The global temperature record is an important indicatorof global climate change, and as a result is a major focus ofattention for climate sceptics.

The El Nio Southern Oscillation (ENSO) involvesabnormal warming (and cooling) of the central andeastern Pacific Ocean. It has impacts around the globe.

Already one of the most widespread and damaging naturaldisasters, drought is likely to affect more people, moreseverely as temperatures increase.

As average global temperatures increase, we are likely tosee more record highs, and fewer record lows. This wouldmake heatwaves longer, more frequent and more intense.

Cold and snowy weather attracts media attention and canhave an impact on public opinion and concern about a

warming world, but it does not disprove climate change.

Climate change will likely make a bad situation worse formany species, and could become the main cause of species

extinction in the future.

Climate change is likely to increase flooding, and givenphysical limits to flood adaptation, emissions reductionsare needed to prevent unmanageable flooding in the future.

A warming world shifts the seasonal activities of plantsand animals, with uncertain consequences.

Wildfire is important to most ecosystems; but higher tem-peratures can alter natural fire-regimes, permanently re-leasing greenhouse gases and amplifying climate change.

50 moRe oN PiRc


4/27

Here we list those who generously donated time

and expertise to answer our awkward questions,

straighten out our confusions or review our writing.

Many kind people helped us with this work in some

way or another; far too many to mention individu-

ally here. Many, many thanks for all your comments,corrections and conversations.

Dr John Abrahams, Dr Lisa Alexander, Prof. JonathanBamber, Dr Eleanor Burke, Dr Mark Cane, Dr MatthewCollins, John Cook, Prof. Kirsten de Beurs, Maria Dick-inson, Dr Stephen Dorling, Prof. Nick Dulvy, Dr ErichFischer, Dr Mike Flannigan, Wendy Foden, Dr LisaGoddard, Dr James Hansen, Prof. Sandy Harrison, DrStephan Harrison, Prof. Katherine Hayhoe, Prof. OveHoegh-Guldberg, Dr Marika Holland, Christian Hunt, DrNat Johnson, Prof. Phil Jones, Dr Alison Kay, Dr Eliza-beth Kendon, Dr Simon Lewis, Prof. Mike Lockwood,Terry Marsh, Dr Jeff Masters, Dr Jerry Meehl, Dr WaltMeier, Dr Annette Menzel, Dr Max A. Moritz, Dr SonNghiem, Dr Camille Parmesan, Dr Verity Payne, Prof.Stuart Pimm, Prof. Colin Prentice, Dr Mike Raupach,Dr Nick Reynard, Dr Jeff Ridley, Dr Reto Ruedy, Dr BenSanter, Prof. Mark Saunders, Dr Gavin Schmidt, DrMarko Scholze, Prof. Richard Seager, Dr Justin Shef-field, Dr Amber J. Soja, Prof. Richard Somerville, Prof.Tim Sparks, Dr Julienne C. Stroeve, Jon Taylor, Dr Ste-

phen Thackeray, Prof. Chris Tho mas, Dr Peter Thorne,Dr Kevin Trenberth, Olly Watts, Prof. Andrew Weaver,

Robin Webster and Dr Chris West.

Rpnby r ny rrr, n r k

y, ur, PiRc.

Wed also like to thank the Network for Social Change,

the Joseph Rowntree Charitable Trust and the 1970

Trust for supporting this work.

thaNKs foRewoRDPIRCs Climate Factsheets are a valuable contribution

to broader public understanding of the present state

of climate science. They clearly and cogently set out

the evidence for anthropogenic global warming - from

rising global temperatures to melting Arctic sea ice -

and its interaction with various climatic events, suchas wildfires, droughts and flooding.

In constrained economic times, it is vital that we do

not lose focus from tackling what remains the most

pressing challenge humanity faces. It falls to policy-

makers, journalists and civil society organisations to

communicate accurately and without bias the threats

we face from a warming planet.

The authors of these Factsheets state clearly what

is known, and what isnt, about the contribution that

human-induced climate change is making to shifting

weather patterns and other observed phenomena. I

commend them to anyone wishing to learn more about

the science of climate change - and particularly to

those communicating climate change to a wider audi-

ence, who need the facts at their fingertips now more

than ever.

sr Jn hugnFormer Co-Chair of the Intergovernmental Panel on Climate Change (IPCC)

Former Director General of the UK Met Office


5/27

suryAverage global temperature has increasedby around 0.75C since the beginning of the20th century. Most of this is very likely to bedue to human greenhouse gas emissions.

All three main temperature data sets agreeon the broad trend, despite slightly differentanalyses.

Each of the last three decades was warmerthan the last. The noughties was the hottestdecade on record.

Long-term, temperatures are rising, but thisdoesnt mean that each year will be hotterthan the last.

cnxEvery January,1 the global average temperaturefor the previous year is announced by three in-dependent organisations. Though a single yearsranking (hottest or not) attracts media attention,only the long-term trend is evidence of climate

change.2

Before climate negotiations in Copenhagen(2009) and Durban (2011), private emails fromthose working on global temperature data werepublished on the Internet (now referred to as Cli-

mategate).3 Since then, nine independent reviewshave cleared the scientists involved and their work

(for more, see:bit.ly/climateg8).4

Whats more, the average global temperature isonly one piece of evidence of a warming world.5Other long-term trends like shrinking Arctic seaice,advancing spring (see p.10 and p.24 respec-tively), glacial retreat, melting permafrost and sealevel rise are consistent with the warming evident

in the temperature record.

Bkgrund nEvery day local temperatures are recorded bythousands of weather stations on land, and onbuoys and ships at sea.6 Though the number ofweather stations has changed over time, todaydata from between 4,000 and 6,000 of theseweather stations are used to calculate average

temperature across the globe.7

Three main organisations independently analyseand process data to perform this calculation:

- GistemP(bit.ly/gistemp) - NASA Goddard Insti-tute of Space Studies (GISS) in the USA.

- hdcRUt(bit.ly/hadcrut) - University of East An-glia Climatic Research Unit (UEA CRU) and theMet Office in the UK.

- NcDc(bit.ly/ncdc_noaa) - National Oceano-graphic and Atmospheric Administration (NOAA)in the USA.

All three records show:

- An overall long-term warming trend, showingan increase of roughly 0.75C (+/-0.05C, so be-

tween 0.7C and 0.8C8) since the beginning of

the 20th century.9 (Other research shows most ofthis is very likely due to human greenhouse gas

emissions.10,11)

- Very similar year-on-year ups and downs,

(natural variations).12 (The El Nio Southern Os-cillation (ENSO, p.14), volcanic and solar activityaccount for most of these. Without them, the

long-term trend is much clearer.13,14)

- That each of the last three decades was warmer

than the last (by 0.15-0.2C on average).15

- That all ten of the hottest years have occurredsince 1998.16

Independent analyses of the raw data have beenconducted by many people, sceptics included.Even the Berkeley Earth Surface Temperature(BEST) project set up following Climategate toresolve criticism of existing temperature analy-ses by starting from scratch show very similar

trends (see bit.ly/bestcomparison ).17 All reason-able methods produce almost identical results. 18

Small differences in results (for example whichyear is recorded as hottest) stem from differ-ences in analyses - differing ways of dealing with

issues in the raw data.19 Some problems will al-

ways remain (hence the +/-0.05C uncertainty20)whilst others can be ironed out, or reduced for

instance:21

- Unrb r pr quy d. Data recording isnot always good. Bad data sometimes simply can-not be used.22 Large amounts of bad data can skewresults unrealistically, though small bits that slipthrough wont have much effect.23

- Drn urrundng.24 The infrastructure in a citymakes it slightly warmer than nearby rural areas the Urban Heat Island (UHI) effect.25 It is colder up amountain than down in a valley next to it. 26 Globally,

temPeRatUReThe global temperature record is an important indicator ofglobal climate change, and as a result is a major focus of atten-tion for climate sceptics.

www.pirc.info/factsheets8

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1850 1900 1950 2000

Global Average Temperature Temperatureanomalyfromaverage between1951-1980.

NOAAGISTemp

NASA

HadCRUTV3

Met OfficeSources:

bit.ly/tempdata

temPeRatURe

9

exprDr J hnnNasa, Usa

Climate models;temperature & satellite

[email protected]

+1 212 678 5500 Gmt -5

Dr R RudyNasa, Usa

NASA temperature record;greenhouse effect

[email protected]

+1 212 678 5541 Gmt -5

Pr. P JncRU, Uea, UK

CRU temperature record;paleoclimate

[email protected]

+44 (0)1603 592090 Gmt

Dr Gvn sdNasa, Usa

NASA temperature record;climate models

[email protected]

+1 212 678 5627 Gmt -5

the UHI has contributed only 0.02C of warming overthe last century.27 To minimise these differences, theraw data are converted into temperature anomalies -a change in temperature from a reference period orbaseline. This change in temperature is similar bothup a mountain and down in the valley next to it; in acity or surrounding rural areas.28

- sr r nrrupd rrd. Old thermometersare replaced with new ones, or with better technol-ogy. Weather stations are closed down, break or aremoved to different sites.29 Interruptions are oftenidentifiable during analysis (for example a suddenjump in temperature), and the record at that stationis calibrated to make it continuous; to make sure anyincrease (or decrease) in temperature is not artifi-cial.30

- Unvn drbun. There are more weatherstations in densely populated areas. The South-ern Ocean, Africa, Antarctica and the Arctic haverelatively patchy coverage.31 We cant change his-tory, instantly move, or buy more weather stationsto get better coverage. Attempts to deal with thisproblem vary:32 GISTEMP assumes the temperatureanomaly in an area without many weather stations(most notably the Arctic) is the same as the nearestweather station (within reason33).34,35 HadCRUT and

NCDC make no such assumption,36

effectively as-suming that the temperature change in these areasis the same as the average. 37 GISTEMP has slightlyhigher estimates of average global temperatures asa result, since Arctic regions in particular have beenwarming faster than the average. For more informa-tion, see bit.ly/datadiff .

w p t prur d unrb.38,39The datais not perfect,40 but many imperfections are ironed

out or reduced,41 and those remaining leave

an estimated +/-0.05C of uncertainty:42 muchsmaller than the observed warming of around

0.75C since the beginning of the 20 th century.43

tr bn n gb rng n 1998 / dd / nury.44,45 Global warming doesnot mean that each year will be hotter than thelast. There is lots of natural variability - daily todecadal ups and downs, caused mainly by other

factors (ENSO, volcanic and solar activity).46,47Short-term flat or cooling periods have happened

before (take a look at the graphic below).48 Long-term, the trend is still on average 0.15-0.2C

warming per decade;49,50 each of the last threedecades have been warmer than the last (for

more info see bit.ly/temperaturetrends ).51

t brvd rng ud by Urbnh ind (Uhi) 52,53r pry dr n.54 Urban, rural, land and oceantemperatures are all rising.55 The UHI effect hasonly a minor impact (roughly 0.02C of the 0.75C

temperature rise over the last century56), and iscorrected for in analyses.57,58 Both poorly-locatedand well-located weather stations show warm-

ing.59 (Sceptics help disprove their own argumenthere: bit.ly/sitelocations )

t r n r bng rry-pkd.60It is true that not all weather stations data areused. However, most of those dropped actuallyshow more warming than those kept including

them would increase the warming trend.61 Analy-ses that use more of the data do not show any sig-

nificant changes in the long term trends.62,63

Also, there is a huge amount of other evidencethat indicates a warming world (some of which is

discussed in other factsheets).64,65

w n yDr Vky Pp(Met Office): The [main 3 tempera-ture] datasets are all independent, and they all

show warming.66

Pr. P Jn(University of East Anglia ClimaticResearch Unit): The fact that 2009, like 2008,will not break records does not mean that globalwarming has gone away. What matters is the un-derlying rate of warming - the period 2001-2007 ...was 0.21C warmer than corresponding values for

the period 1991-2000.67

Pr. my an(University of Oxford): Even inthe 80s [2008] would have felt like a warm year ...For Dickens this would have been an extremely

warm year.68

Dr Gvn sd(NASA): for any individual year,the ranking isnt particularly meaningful. The dif-ference between the second warmest and sixth

warmest years, for example, is trivial.69 (Thedifference is a few hundredths of a degree centi-

grade.70)

Dr Jn R. cry(University of Alabama), a long-time sceptic, acknowledges: Long-term climatechange is just that, long term, and 12 months of

data are little more than a blip on the screen.71

fr r n

t n nGistemPbit.ly/gistemp

t m o: Gbrng g n (2008)bit.ly/warminggoeson

[PDF; Archive]

Drn d ny rndbit.ly/temprecord

w d y
http://bit.ly/climateg8http://bit.ly/climateg8http://bit.ly/climateg8http://bit.ly/gistemphttp://bit.ly/hadcruthttp://bit.ly/ncdc_noaahttp://bit.ly/ncdc_noaahttp://bit.ly/bestcomparisonhttp://www.pirc.info/factsheetshttp://bit.ly/tempdatamailto:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/datadiffhttp://bit.ly/temperaturetrendshttp://bit.ly/sitelocationshttp://bit.ly/sitelocationshttp://bit.ly/gistemphttp://bit.ly/warminggoesonhttp://bit.ly/temprecordhttp://bit.ly/temprecordhttp://bit.ly/warminggoesonhttp://bit.ly/gistemphttp://bit.ly/sitelocationshttp://bit.ly/temperaturetrendshttp://bit.ly/datadiffhttp://bit.ly/tempdatahttp://bit.ly/bestcomparisonhttp://bit.ly/ncdc_noaahttp://bit.ly/hadcruthttp://bit.ly/gistemphttp://bit.ly/climateg8mailto:[email protected]:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


6/27

suryThe Arctic is warming roughly twice as fast asthe global average.

The long-term decline of Arctic sea ice is dueto rising temperatures. This long-term decline

reinforces natural variability in record lowyears.

Even when a record low in sea ice occurs, thelong-term trend is still most indicative ofclimate change.

The Arctic is changing faster than predictedby the IPCC in 2007. As a result, projectionsof ice-free Arctic summers have beenbrought forward.

cnxIn 2007, sea ice extent reached a dramatic recordminimum, 23% below the previous record.1 Thiscaused considerable alarm among some Arcticscientists, leading to statements such as: the

Arctic is screaming,2 [its] in its death spiral3

and the canary has died.4 Others, such asVicky Pope at the Met Office and science blog-

ger William Connolley, were more cautious.5,6They pointed to natural variability (year-to-yearchanges in weather or ocean currents and cycles)as a possible cause of the record decline.

Since 2007 the minimum moved closer to thelong-term trend, as Connolley and Pope sug-

gested it might. A decline in both maximum 7 andminimum extent (the highest and lowest areascovered by sea ice in a particular year, respec-tively) can be seen in the long-term trend (seegraphic below). The minimum has been dropping

at a rate of roughly 13% per decade since 1979. 82011 was the second lowest recorded sea ice ex-

tent.9

Bkgrund nThe Arctic is warming around twice as fast as theglobal average, largely due to an amplifying (or

positive) feedback.10,11 Losing bright reflectiveice leads to more heat being absorbed by darkerocean surfaces, and more regional warming,which in turn leads to more ice melt. This doesntnecessarily mean it is a runaway process, or thatit might reach a tipping point.12 The extra amount

that melts because of the less reflective surface isonly a small fraction of the initial melt - it adds up

much like interest on a bank account.13

Arctic sea ice is affected by a combination ofocean currents and weather patterns (tem-perature, wind, cloud cover etc.) as well as the

increasing influence of climate change.14 Its notjust the area (or extent) of ice that is affected -recurrent melting means that seasonal ice isntable to build up thickness, a process which takes

a number of years.15 It is therefore more vulner-able to fluctuating weather conditions, since itbecomes easier for small changes to melt the

reflective ice, supplementing the feedback.16

Because of these interactions, there is debateabout whether ice extent (a measurement of sur-face area with greater than 15% ice, most com-monly used), area, thickness, volume or age is thebest measure or predictor of its future behaviour.However, the overall thickness (and hence vol-ume) of the sea ice is also falling (for more info,

see: bit.ly/icemetric ).17 By 2009 only 10% of theArctic ice was more than two years old, compared

to 30% on average between 1981 and 2000. 18

The 2007 IPCC report said summer sea ice isprojected to disappear almost completely towards

the end of the 21st century.19 In 2009, the Copen-hagen Diagnosis, published by 29 leading climatescientists (including several IPCC authors) up-dated this forecast, noting that:

The observed summer-time melting of Arcticsea-ice has far exceeded the worst-case projec-tions from climate models of the IPCC AR4... Thewarming commitment associated with existingatmospheric greenhouse gas levels means it isvery likely that in the coming decades the summerArctic Ocean will become ice-free, although the

precise timing of this remains uncertain. 20,21 (toread more: bit.ly/sensitivearctic )

Latest observations show Arctic sea ice is melt-ing at least twice as quickly as computer simula-

tions suggested,22-24and is unprecedented over

the last 1450 years.25 Model runs now predictthe Arctic being ice-free (in the summer) around40 years earlier than scientists predicted before2007.26,27

aRctic sea iceThe Arctic contains a thin, vulnerable layer of sea ice whichreaches a minimum every September, providing a regular op-portunity to highlight the impacts of climate change.


Arctic Sea Ice Extent Maximum& Minimum,1979-2011

m km2

Source: NSIDC, bit.ly/seaicedata

Record low, 2007

Trend

Trend

aRcticseaice

11

exprDr J Rdym o, UK

Sea ice models

[email protected]

+44 (0)1392 886472 Gmt

Dr mrk hndNcaR, Usa

Sea ice models & history

[email protected]

+1 303 497 1734 Gmt -7

Dr sn NgNasa, Usa

Sea ice thickness & age

[email protected]

+1 818 354 4321 Gmt -8

Dr Junn srvNsiDc, Usa

Sea ice; satellites; albedo

[email protected]

+1 303 492 3584 Gmt -7

w p ar rvrng.28 Just because thereisnt a new record low, this does not mean that thelong-term trend has changed. Arctic sea ice is still

in decline; there is no evidence of recovery. 29,30

Furthermore, as explained above, the sea ice ismelting much faster than expected, which has ledto predictions of an ice-free Arctic being brought

forward by roughly 40 years.31

i n u: nur vrby / nd.32,33 There is a lot of natural variability in theArctic, but this cant explain the long-term trend.The only explanation for this trend is warmingcaused by increased atmospheric concentrationsof CO2 - a clear and distinct human fingerprint on

long-term Arctic sea ice melt.34

i undrr vn.35 There are volcaniceruptions under the Arctic, but the heat doesntreach the surface, and theres nowhere near

enough of it to melt all the ice. 36

tr n 1930.37 Satellite re-cords began in 1979. To know what happenedbefore then scientists have analysed a variety ofdifferent shipping records and historic accounts.Analysis of Russian ice charts and other data setsshows Arctic sea ice minima over the last decadeare lower than those in the 1930s and 1940s (see

bit.ly/arctichistory ).38

w n yDr Vky Pp(Met Office, UK): The record-break-ing losses in the past couple of years [2006-7]could easily be due to natural fluctuations in theweather, with summer ice increasing again over

the next few years.39

Dr Gvn sd(NASA Goddard Institute forSpace Studies, USA): the Arctic is a good reminderthat uncertainty in model projections cuts both

ways.40

Dr J ovrnd(National Oceanic andAtmospheric Administration): The melting is hap-pening faster in the real world than it has in the

models.41

Dr td sb(National Snow and Ice DataCentre, USA): The main message is not so muchwhether or not we set a record, but this year[2011], without any noticeably unusual pattern ofweather, we nearly broke a record, which only fouryears ago took a very unusual weather pattern

plus a warming Arctic to achieve.42

Dr crp Knnrd(Centro de Estudios Avan-zados en Zonas Aridas, Chile): This drastic andcontinuous decrease [in Arctic sea ice] wevebeen seeing from the satellites does seem to beanomalous... It does point to a continuation of this

trend in the future.43

Dr w mr(National Snow and Ice Data Centre,USA): If we get another warm year, anything like2007, then the ice is really going to go. And the

chances are that at some point in the next fewyears we are going to get a warm one. 44 fr r n

Nn sn nd iD cnr (NsiDc)ar s i faQbit.ly/arcticfaq

w ud dr- n 2007bit.ly/2007causes

UNeP c cngcpndu p.17-20bit.ly/climatecompendium

l N (NsiDc)bit.ly/arcticnews

w d y
http://bit.ly/icemetrichttp://bit.ly/sensitivearctichttp://bit.ly/sensitivearctichttp://www.pirc.info/factsheetshttp://bit.ly/seaicedatamailto:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/arctichistoryhttp://bit.ly/arcticfaqhttp://bit.ly/2007causeshttp://bit.ly/climatecompendiumhttp://bit.ly/arcticnewshttp://bit.ly/arcticnewshttp://bit.ly/climatecompendiumhttp://bit.ly/2007causeshttp://bit.ly/arcticfaqhttp://bit.ly/arctichistoryhttp://bit.ly/seaicedatahttp://bit.ly/sensitivearctichttp://bit.ly/icemetricmailto:[email protected]:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


7/27

suryDrought happens all around the world, thoughits impacts can be reduced and are not alwayssevere.

Severe drought, however, directly affects food

and water availability, and can kill.Globally, since the 1970s, droughts are gettinglonger and more widespread, but only perhapsslightly more severe.

Drought projections are still not very accurate,largely because they rely heavily on uncertainprecipitation projections.

Higher temperatures cause more evaporationfrom land which will exacerbate drought in thefuture.

cnxDrought is one of the costliest and most wide-spread natural disasters.1 Long droughts reducereservoir levels, limiting or cutting off water sup-plies for drinking and agriculture.2 Drought cancause crop failure, leading to famine locally, andrising food prices globally.3 Those dependent onlocal land for food and water are most affectedby drought, and usually have the least capacity toadapt.4 Drought can, and does, kill.5

Comparatively, the direct impacts of even severedroughts in the UK (for example 1976, 1995-9 6)are mild. Drought can diminish water supplies foragriculture and peoples health can suffer, espe-cially when there is also a heatwave (as in 2003).7However, winter rainfall helps keep reservoirsrelatively full during summer droughts,8 and regu-

latory measures, like hosepipe bans, save waterfor more important uses.9,10 In the UK, droughtsare not usually severe or long-lasting.11

Bkgrund nDrought describes abnormally dry conditionscaused by below-normal precipitation (rain, hail orsnow) over months or years.12,13 It happens even inwet regions because it is defined relative to localconditions. 14 Deserts dont necessarily experiencedrought because they are always dry.15Droughtseverity depends on how dry it is (intensity), howlong it lasts (duration) and how much area it cov-ers (size).16,17

The direct impact of climate change on drought ishard to estimate because:

- murng drug rd.18 Groundwater andreservoir levels, river flows and soil moisture all

help measure drought.19 But these records areoften short and poorly spread out. Precipitationand temperature data for basic water-in, water-out calculations20 are more comprehensive, butover-simplify the situation dryness doesntalways mean drought.21

- sng drug v ngd du.Droughts change in severity and frequencyyear-to-year and decade-to-decade.22They areregional, and happen relatively infrequently,meaning there may be insufficient data to showany pattern or trend.23

- mny r nrbu drug. Some fac-tors may be influenced by climate change andnatural variations (El Nio Southern Oscillation(see p.14), or monsoons), such as:24,25

- Local rainfall.

- Low levels of snowfall (which can cause delayeddrought as less spring meltwater flows down riv-ers).26

- High local temperatures (which increase evapora-tion, removing water 27,28).

Other factors are hardly influenced by climate:

- Irrigation systems and dams diverting watercourses.29,30

- Land use change or erosion (which can cause morewater to evaporate or run-off).31,32

- How many people require water and what they needit for (increasing demand can mean supplies fallshort.)33,34

Since different combinations of these factorsinteract to create the particular conditions of adrought, the impact of climate change can bedifficult to identify.

However, some changes to drought have beenidentified:

- Globally, the area affected by serious droughthas increased since the 1970s,35,36 and someevidence suggests that droughts are intensifying,though not by much.37-39

- Regionally, since the 1970s, droughts in partsof Africa and East Asia have become more se-vere, and those in southern Europe and easternAustralia have experienced slightly severerdroughts.40

- These areas have dried significantly since the1950s, with the Sahel (south of the Sahara) mostseverely affected (see graphic below).41 Evapora-tion has contributed a small amount to dryingsince the 1980s.42,43

These changes, however, have not been clearlyattributed to climate change.

DRoUGhtAlready one of the most widespread and damaging natural dis-asters, drought is likely to impact more people, more severely,as temperatures increase.


.20 .16 .12 .08 .04 0 .04 .08 .12 .16 .20

Trend (% yr1)

Annual Volumetric Soil Moisture

Source:Sheeld,Justin; Wood,Eric F.

(2008)Global TrendsandVariabilit yin SoilM oisture andDrought Charac-

teristics,1950 2000,Journal of

Climate,vol.21,issue 3,p.432.

Statistically significant trends, 19502008

DRoUGht

13

exprDr Jun sdPrnn Unvry, Usa

Water cycle; drought &flooding extremes

[email protected]+1 609 258 1551 Gmt -5

Pr. Rrd sgrcub Unvry, Usa

Climate variability;multi-year droughts

[email protected]

+1 845 365 8743 Gmt -5

trry mrcnr r egy ndhydrgy, UK

Hydrology; drought;flooding

[email protected]

Dr sn lUnvry ld, UK

Tropical forests; theAmazon rainforest

[email protected]

+44 (0)113 3433 337 Gmt

c dbk

Higher temperatures increase evaporation fromland, which in drier areas can increase tempera-tures further (a reinforcing or positive feedback) less heat is lost through evaporation becausethere is less moisture in soils, and more heatcomes in because fewer clouds form.44,45

Drought also causes vegetation to dry out and die,and can lead to fires.46 These release CO2, whichcan enhance climate change (another reinforcingor positive feedback).47 Die-back in the Amazon,caused by severe droughts in 2005 and 2010 (bothonce-in-a-hundred-year droughts 48) releasedmore CO2 than the Amazon usually absorbs in ayear (seebbc.in/amazondrought ).49,50 In the long-term, if sufficiently sensitive to drought, the Ama-zon could change from a sink to a source of CO251though this may not be permanent.52

Prjn

In general as global (and local) temperatures in-crease, drier areas are expected to dry further. 53,54

Some research suggests that droughts will there-fore become longer and more widespread, and be

more severe.

55,56

Evaporation will likely play a big-ger role under higher temperatures, which someresearch suggests will lead to droughts muchmore severe than ever recorded.57 Lower or lessfrequent precipitation will still be the dominantfactor increasing drought in the future.58

More specific local (or regional) drought projec-tions are quite uncertain.59 The precipitationprojections on which they rely include naturalvariations such as ENSO and monsoons, whichare currently difficult to predict.60,61

w p Drug v ppnd br62,63nd r(rr) nur.64,65The direct cause of adrought is the particular conditions of the region,

which include natural factors.66 Climate change,however, will likely play a larger part in droughtas precipitation patterns change and higher tem-peratures enhance evaporation.67

fdng nd rn n drug prjn rrng.68 More severe or frequent droughts donot necessarily mean there will be no rain;69 andshort-term events are different from long-term

trends.70

tr r nrdry prjn.71 Many local

(or regional) precipitation projections are still not

very certain, and may change as we learn more.72Generally, drying regions are likely to continuegetting drier, but the specifics are harder to pre-dict.73

w n dp gruur b r drug r-n n prb.74 To an extent, watermanagement and food production can be adapted

to be more drought resilient.75 However, manysimply do not have the resources to adapt, and themore frequent and severe drought becomes, the

harder it is to maintain such measures.76

Drug r n bng r rqun,r vr r ngr.77 Droughts are relativelyrare and so the quantity of data is small, making

identifying trends difficult.78 Some strong dryingtrends have been established (for example in the

Sahel),79 and there is evidence that shows droughtbecoming longer and hence more severe in some

areas.80-82

t iPcc rng bu azn.83 Ama-zongate was widely reported in the media.84,85

The IPCCs 2007 report said that Up to 40% of theAmazonian forests could react drastically to evena slight reduction in precipitation,86 referencinga non-peer-reviewed WWF report. However, inde-pendent scientific studies concluded the same or

worse.87-89For more info - bit.ly/amazongate ..

w n yDr sn l(Leeds University, UK): If eventslike this [severe drought in 2010] happen moreoften, the Amazon rainforest would reach a pointwhere it shifts from being a valuable carbon sinkslowing climate change, to a major source of

greenhouse gases that could speed it up.90

Pr. i hd(National Oceanic and Atmos-pheric Administration, USA): There is a hint thatthe current drying may be caused by what themodels suggest [climate change], but its only a

hint right now.91

Pr. t Rr (University of Utah, USA)There is a lot of natural variation from year toyear [in the drying of the higher latitudes], but we

see a slow, gradual change.92

Pr. svn Runnng(University of Montana,USA) Globally, were seeing larger and longer

droughts.93

fr r n

Drug - dy ndrrbit.ly/futuredrought

h vr drug,nd d nbit.ly/droughtmeasures

currn drug unn UKbit.ly/ukdroughtnow

w d y
http://www.pirc.info/factsheetsmailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://bbc.in/amazondroughthttp://bbc.in/amazondroughthttp://bit.ly/amazongatehttp://bit.ly/futuredroughthttp://bit.ly/droughtmeasureshttp://bit.ly/ukdroughtnowhttp://bbc.in/amazondroughthttp://bit.ly/ukdroughtnowhttp://bit.ly/droughtmeasureshttp://bit.ly/futuredroughthttp://bit.ly/amazongatemailto:[email protected]:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


8/27

suryENSO is a major part of the natural variabilityof the Earths climate.

Comparatively frequent El Nios (warmphases) likely contributed a small amount

to global warming between 1976 and 1998.A possible shift to more frequent La Nias(cool phases) may have moderated warmingsince.

The effects of climate change on ENSO areincredibly difficult to identify because it is suchan irregular cycle.

We dont know yet how climate change mightaffect ENSO in the future, though it will likelyintensify some of the impacts.

cnxENSO is a natural, irregular cycle that has hap-

pened for thousands of years.1 No link to climate

change has been definitively established.2,3 Thereare, however, similarities between ENSO and cli-mate change:

- Prdn: Though ENSO processes are notentirely understood, its general behaviour andpatterns are predictable.4,5 Specific regional im-

pacts can be difficult to predict.6,7

- ip: ENSO affects temperature and precipi-tation patterns globally. It changes the likelihoodof floods, droughts and tropical storms/hurri-

canes in different areas.8

- arbun: While it is difficult to explicitly labelindividual extreme events as being caused by El

Nio or La Nia, they are strongly linked.9

However, the impact of ENSO only lasts for theduration of the cycle (a few months to two years),

or with a small delay.10 Changing somewhat ir-regularly year-to-year, it is responsible for muchof the noise (or natural variation) in various cli-

mate indicators.11

Bkgrund nENSO involves an interaction between ocean and

atmosphere in the tropical Pacific Ocean.12 A LaNia (the cool phase of ENSO) is a stronger ver-sion of normal (or ENSO neutral) conditions: amore intense cooling of the central and eastern

Pacific Ocean. El Nio (the warm phase of ENSO)refers to an abnormal warming of these areas

of Pacific Ocean.13 The ocean warming causesa change in the winds, which in turn causes achange in the ocean surface temperatures, rein-forcing the initial warming - a positive feedback

which builds El Nio.14,15

The change between El Nio and La Nia issomewhat erratic: the two phases occur at irregu-lar intervals of two to seven years, lasting between

a few months and two years.16,17 There can be sev-eral El Nios or La Nias in a row, with neutralconditions in between (see graphic below). Thestrength of an El Nio or La Nia varies signifi-

cantly.18

ENSO forecasting models can predict El Nio orLa Nia six-to-nine months in advance by recog-

nising ocean temperature patterns.19 It is moredifficult to predict the strength20 or specific localimpacts of a phase, because ENSO behaves in-consistently.21,22 It is not entirely understood what

initiates or ends the reinforcing feedback.23

Gb ip

ENSO (El Nio and La Nia on average) has likelycontributed about 0.06C to global warming since1950.24 El Nio contributions to individual yearscan be larger. 1983 and 1998 featured super El

Nios far stronger than previously recorded.25 Thesuper El Nio of 1998 (the hottest year in the Met

Office record26) likely contributed 0.17C of warm-

ing to that year.27 An El Nio causes a temporary

increase in global average temperature for tworeasons: 28

1. Rdrbun : a larger portion ofthe surface of the Pacific Ocean is warmerthan normal, so there is more evaporation.This transfers heat from the ocean to theatmosphere.

2. ennd grnu : more evapo-ration also means more water vapour (also agreenhouse gas), which reinforces this effect- another positive feedback.

With La Nia, a larger portion of the surface of thePacific Ocean is cooler than normal, so there isless transmission of heat from the ocean into the

atmosphere.29 Despite this, 2011 was the warmestLa Nia year ever recorded (for more information

see: bit.ly/2011lanina).30

el NioThe El Nio Southern Oscillation (ENSO) involves abnormal warming (or cool-

ing) of the central and eastern Pacific Ocean, brought about by interactions

between the ocean and the atmosphere. It has impacts around the globe.


-2

-1

0

1

2

3

ENSO Index

Source:NOAAsOceanicNia Index, see: 1.usa.gov/ensodata

El Nio La Nia ENSO Neutral

1960 19801970 1990 20101950 2000

elNio

15

exprPr. mrk sundrUcl, UK

Climate variability; ENSO;seasonal forecasting

[email protected]+44 (0)1483 204187 Gmt

Dr m cnm o, UK

ENSO in climate models;ocean-atmosphereinteractions

[email protected]

+44 (0)1392 723984 Gmt

Dr l GddrdiRics, Usa

Near-term climate change;forecasting

[email protected]

+1 845 680 4430 Gmt -5

Dr Kvn trnbrNcaR, Usa

Natural variability; ENSO;atmosphere; hurricanes

[email protected]

+1 303 497 1318 Gmt -7

ENSO focuses weather in particular areas. Ef-fects are most severe in the equatorial Pacific,tropics and Pacific rim countries:

- Prpn: El Nio is linked to heavy rainfalland flooding along the western coast of SouthAmerica, and drought in Indonesia, India and

Australia.31,32La Nia has opposite, though not

necessarily equal effects.33,34

- sr: La Nia tends to bring more hurri-canes, typhoons and tropical cyclones over theAtlantic and Gulf of Mexico. El Nio suppressesthem along the eastern coast of North America,and increases storm activity over the Pacific

Ocean. 35-37

ENSO also affects parts of East and South Africa,

and parts of Asia; 38 it has only minor impacts inEurope and the UK. It can be difficult to untanglethe effects of climate change and ENSO. BecauseENSO is irregular, it is difficult to tell if there are

changes due to global warming.39 Some evidencesuggests a link to the increasing intensity of thefloods and droughts associated with ENSO (see

p.12 and 14 respectively).40 Climate models disa-gree on the future effects of climate change onENSO - some predict stronger phases, some

weaker and others no change.41-44 Because ENSOinfluences global weather patterns so strongly,it is one of the reasons there is uncertainty in re-

gional projections of climate change. 45

w p Gb rng du e N. 46-48 El Niodoes temporarily enhance the global averagetemperature. But ENSO cycles are short - a fewyears maximum.49 ENSO has likely contributedonly 0.06C to the 0.55C increase seen in globalaverage temperatures since 1950 (note the total

warming since 1900 is roughly 0.75C50 -

see p.8).

51-53

c d r unrb bu yn u eNso.54 Climate models simu-late ENSO well on a global scale,55 but are often

less accurate regionally.56 There is disagree-ment on how (or if) ENSO might change in the

future,57,58but greenhouse gases have, and willlikely continue to be responsible for most of the

warming,59,60 meaning global projections are stillreliable.

Gb rng ppd n 1998.61 The Met Officestates that 1998 was the hottest year on record.62Some claim wrongly (see p.8) that this meansglobal temperatures have been falling since

then.63 In 1998 there was a super-El Nio, whichgave an extra boost to temperatures, on top of the

long-term warming.64 Global average tempera-tures in 2010 and 2005, were very close to 1998 despite being unaided by any superEl Nio.65,66

w n yJn ck (Skepticalscience.com) : Data analysis,physical observations and basic arithmetic allshow ENSO cannot explain the long-term warm-

ing trend over the past few decades.67

Dr wnju c(Commonwealth Scientific and In-dustrial Research Organisation, Australia): Whilethe possibility of large changes in ENSO cannotbe ruled out, research conducted to date does notyet enable us to say precisely whether ENSO vari-ability will be enhanced or moderated, or how the

frequency of events will change.68

m Jrrud(Secretary-General of the WorldMeteorological Organisation): La Nina is part ofwhat we call variability. There has always beenand there will always be cooler and warmer years,but what is important for climate change is thatthe trend is up; the climate on average is

warming.69

fr r n

a eNso-rd nbit.ly/ensoinfo

tp npnbu e N xpndbit.ly/topmisconceptions

e N nd gbrng n R cbit.ly/whatisenso

Nn-n e Nxpnnbit.ly/nontechy

w d y
http://bit.ly/2011laninahttp://bit.ly/2011laninahttp://www.pirc.info/factsheetshttp://1.usa.gov/ensodatamailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/ensoinfohttp://bit.ly/ensoinfohttp://bit.ly/topmisconceptionshttp://bit.ly/whatisensohttp://bit.ly/nontechymailto:[email protected]://1.usa.gov/ensodatahttp://bit.ly/nontechyhttp://bit.ly/whatisensohttp://bit.ly/topmisconceptionshttp://bit.ly/ensoinfohttp://bit.ly/2011laninamailto:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


9/27

suryIdentifying the influence of climate changein observations is difficult because manyfactors contribute to flooding.

However, it is likely that climate change will

contribute to flooding from rising sea levels,melting glaciers and by intensifying rainfall.

In parts of the Northern Hemisphere, climatechange has contributed to more intenseheavy precipitation since the 1950s.

Multiple factors likely contributed to asubstantial global increase in large floods overthe 20th century.

cnxFloods affect roughly 140 million people everyyear more than all other natural disasters put

together.1 They contaminate drinking water, ruinharvests and wash out fertilizers and nutrientsfrom soil; water-logged fields rot food and spread

crop diseases, prolonging famine.2 Stagnant watercontaminated with sewerage, fertilizers and oilspread water-borne diseases like typhoid, cholera

and diarrhoea.3 Floods interrupt power supplies,communications and transport; they damage

homes, property and infrastructure.4 Floods can

also trigger landslides.5 Many impacts will worsenas temperatures continue to rise.6

If flood risk continually increases, adaptive meas-ures become obsolete there are limits on howhigh we can build flood defences, for example

we cant play catch-up forever.

7

British peopleexposed to flooding regard climate change asmore concerning and less uncertain, even if theflood cannot be attributed to climate change. Theyalso feel that their actions will have an effect on

climate change and are more prepared to act. 8

Bkgrund nIncreasing temperatures affect flooding directly:

- Rising sea levels (from melting land ice, andocean expansion due to warming), in combina-tion with cyclones and high tidal surges, in-

crease flood risk.9

- Melting glaciers put pressure on watercourses

downstream which can cause flooding.10

and indirectly:

- By encouraging evaporation and reducing con-

densation, the atmosphere is able to hold more

water.11 This is like fuel for weather systems, 12-15increasing the chances of more intense precipi-tation which, given the right conditions, meansmore flooding.16 Atmospheric water vapour hasincreased by 5% over the 20 th century, in line

with what basic physics expects from the ob-served temperature rise.17-19

But identifying the influence of climate change in

observations is difficult, for several reasons:20

- murng dng rd. Direct measure-ments of flooding, and factors that influenceflooding (heavy precipitation, continuous wetperiods, glacier-melt, sea level rise, river flow,water run-off from land) are often short-termor only cover small areas.21 Changes in thesefactors dont necessarily mean more or lessfloods.22 Measuring economic damages fromflooding can include changes in population,wealth and infrastructure on floodplains and incoastal areas, rather than just changes in flood-ing.23,24

- fndng rnd du. Floods are regionaland happen relatively infrequently, makingtrends hard to identify.25 Long-term trendscan be hidden by significant year-to-year anddecade-to-decade variation.26,27 Average precipi-tation need not change much for more floods tooccur the same amount of rain might fall inmore intense but sporadic events, increasing thelikelihood of flooding.28

- mny r nrbu drn yp d. Local precipitation and water availabilitycan be influenced by climate change but alsodepend on atmospheric circulations,29 naturalcycles like the El Nio Southern Oscillation (seep14), and monsoons.30 Human factors like land-use change, water management and irrigationhave all affected watercourses; agriculture,deforestation, loss of flood plains, and urbanisa-tion can all affect the likelihood or severity offlooding.31

- arbun ng rd.32,33 Theimpact of climate change on, or amongst, themultiple factors that create the particular cir-cumstances of a flood (or a trend in flooding)can be difficult to identify.34,35 It is difficult to saythat climate change is the cause of a flood, butit can affect the likelihoodof one for exampleone study found that the floods in the UK in 2000

flooDiNGClimate change is likely to increase flooding, and given physicallimits to flood adaptation, emissions reductions are needed toprevent unmanageable flooding in the future.


Changes in Annual Precipitation 1951-2000

mm/day

-4 -2 -1 -0.5 -0.3 -0.1 0.1 0.3 0.5 1 2 4

Change in globalannual precipitationwhen averaged overthe whole worldbetween 1951-2000is only -0.03mm/day.

Source: NASA,1.usa.gov/precipmap

flooDiNG

17

exprDr N JnniPRc, Usa

Climate variability; ENSO;extreme weather;

[email protected]

+1 808 956 2375 Gmt -10

Dr ezb Kndnm o, UK

Extreme rainfall; precipita-tion projections; modelling

[email protected]

+44 (0)1392 884 760 Gmt

Dr an Kyceh, UK

Water; flooding andclimate change

[email protected]

+44 (0)1491 838 800 Gmt

Dr Nk Rynrdceh, UK

Flood risk; flood projections

[email protected]

+44 (0)1491 838800 Gmt

were twice as likely to have happened because ofclimate change.36,37

UK

|n the UK, floods have become slightly more fre-quent over the last 30-40 years,38-40 as have longer

periods of rainfall (a major cause of flooding).41Over the 20th century, winter rain has been moreflashy (falling in more sporadic, but intense peri-

ods), though in summer the opposite is true.42 Allof these changes, however, are small and at pre-

sent indistinguishable from natural variations.43

Very generally, the north of the UK is likely to getwetter in winter, the south drier, though the reli-ability of such specific regional projections is low

(see bit.ly/ukprecip for more info].44

wrd

Globally, large floods have become substantially

more frequent over the 20th century,45 with largeinland floods twice as frequent per decade be-

tween 1996 and 2005 as between 1950 and 1980. 46Some of this is likely due to better reporting andchanging land use.47

The number of heavy precipitation days 48 and

sudden downpours49 has increased over thelast half of the 20 th century in many areas of theNorthern Hemisphere. Though total or averageprecipitation may not have changed much, evi-dence suggests climate change is causing it to fallin more intense bursts.50,51All these trends are

likely to continue.52

These observations have been at the upper endof IPCC projections, suggesting that modelsmay be underestimating intense precipitation

increases.53,54 Future projections vary widely andfew robust regional projections have been made.Generally, higher latitudes will become wetter,

making flooding more likely.55,56 However, becauseflooding is very localised, and depends on manyfactors, it is hard to say where and when floodsmight be more or less common.

w p fdng n ud by ng.57Climate change affects some of the factors thatcause, and can exacerbate flooding - by concen-trating or intensifying precipitation; and by melting

land ice and warming oceans, contributing to sea-level rise.58

tr v y bn d.59-61 Large floodshave become substantially more frequent globallyover the 20th century, as wed expect in a warmingclimate, and they will likely become even more

frequent as temperatures increase. 62

Rn n nrd, nd n nr.63Averagerainfall doesnt have to change that muchfor there to be an increase in flooding. If the sameamount of rain falls in shorter, heavier events,

floods are more likely.64

inrd dg r dng r du r pp vng nd budng n d pn.65As well as these social factors, bigger, more fre-

quent floods increase damages,66,67 and due toclimate change will likely play a bigger role in the

future.68

Yu n b drug andd n ng.69 Observations already show an increase

in extreme precipitation and in drought, thoughin different places (see graphic below).70 Gener-ally, wet places will get wetter (and make floodingmore likely), and dry places will get drier (making

droughts more likely).71

w n yPr. in cuk(University of Bristol, UK): Tenper cent of UK housing is on flood plains, but thisis quite low compared to some countries it is

70% in Japan and 100% in the Netherlands.72

Dr Kvn trnbr(National Center for Atmos-pheric Research, USA): There is a systematic in-fluence on all of these weather events now-a-daysbecause of the fact that there is this extra watervapor [sic] lurking around in the atmosphere ...

this is one manifestation of climate change. 73

Pr. sn Rr(Potsdam Institute forClimate Impact Research, Germany): Looking onlyat individual extreme events will not reveal theircause, just like watching a few scenes from a

movie does not reveal the plot.74

Dr andr wvr(University of Victoria, Canada):We should continue to expect increased floodingassociated with increased extreme precipitationbecause of increasing atmospheric greenhouse

gas.75

fr r n

Gr pur d (2001-prn)bit.ly/floodimages

a ury rrng un n rnbit.ly/humaneffect

fd nurn nd ngbit.ly/flood-insurance

w d y
http://www.pirc.info/factsheetshttp://1.usa.gov/precipmapmailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/ukpreciphttp://bit.ly/floodimageshttp://bit.ly/humaneffecthttp://bit.ly/flood-insurancemailto:[email protected]://1.usa.gov/precipmaphttp://bit.ly/flood-insurancehttp://bit.ly/humaneffecthttp://bit.ly/floodimageshttp://bit.ly/ukprecipmailto:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


10/27

suryBoth natural cycles and climate change cancontribute to the local high-temperatureperiods of a heatwave.

Local temperatures during the heatwaves in

Europe (2003) and in Russia (2010) were muchhigher than extremes for these places over thelast 510 years.

Globally, heatwaves on average have becomeslightly hotter and more frequent.

This trend is likely to continue, with recordheatwaves experienced more often in some

areas.

cnxRecent heatwaves in Europe (2003) and Russia(2010) were literally off the scale, with tempera-tures significantly higher than the extremes

of the last 510 years,1 and had less than a one-in-750 chance of occurring naturally in the climate

a few decades ago.2,3 Climate change projectionssuggest heatwaves like these will become morecommon in the future if we do little to mitigate

climate change:4 they may be the norm by the

2040s,5,6 with a possibility that by the end of thecentury, 2003 would be a cool year (Dr Myles

Allen, Oxford University, UK).7

Historically, the UK has rarely experienced se-verely high temperatures, but projections suggestwe too will have longer, hotter and more frequent

heatwaves in the future.8 Currently, planning tocope with heatwaves is not a major part of centraland local government policy, especially outside

the healthcare sector.9 A recent UK survey ofthose most at risk from heatwaves (the elderlyand unwell), found they hugely underestimated

the danger of a heatwave.10

Bkgrund nTypically, a heatwave is declared once it has beenhotter than a particular temperature for a number

of days, though there is no universal definition.11

ip

A heatwave has detrimental effects on human life,

regional economies and ecosystems.12 Anythingthat is used to near-constant temperatures, orthat functions near its temperature limits, is vul-

nerable to heatwaves.13

Heatwaves with hot nights (as well as days) aremore dangerous as there is no respite from the

heat.14 Humid heat is more dangerous than dry

heat,15 as it is more difficult to cool down by

sweating.16 Even in dry heat, we rarely survivetemperatures that stay higher than 45C for

long.17 Less severe heatwaves can and do kill through heat exposure, or by aggravating pre-

existing conditions.18 The very young, elderly and

unwell are at most risk.19,20Air pollution in cities

intensifies the impacts of a heatwave.21,22Changesto behaviour (using air conditioning or resting dur-ing the hottest hours) and early warning systems

can reduce the impact.23-25

Knock-on effects such as damage to vegetationfrom excessive heat, drought or wildfire could act

as reinforcing (or positive) climate feedbacks,26-28and can kill by affecting local food and watersources, or by increasing global food prices, asin Russia in 2010 (seeDrought, p.12 andWildfires,

p.26 for more on these points).29

N xr

Peak temperatures are rising much faster than

averages,30 in line with climate model predic-

tions.31 Extremely hot days are becoming hotterand more frequent, making heatwaves more

likely.32,33 Globally, there has been an observable

increase in the frequency of heatwaves.34 Sincethe 1950s, heatwaves have been lengthening in

some places (central and eastern Europe,35,36

Alaska, Canada, Siberia, central Australia 37); but

shortening in others (south-eastern USA, easternCanada, Iceland and southern China).38,39

Local temperatures are influenced not only byclimate change, but by cycles such as El Nio (seep.14) and atmosphere and ocean circulations thatpromote high-pressure systems. This makes at-tributing any heatwave to climate change difficult,because both climate change and natural factors

contribute.40 New research can, however, tell ifclimate change has made a heatwave more likely for example, the 2003 European heatwave wasat least twice as likely because of warming caused

by human greenhouse gas emissions.41 Thereis only a 20% chance that the Russian heatwavein 2010 would have happened without climatechange, and records like this are now five times

as likely.42

Europe (2003) and Russia (2010) experienced thehottest heatwaves of the past 510 years, far out-

heatwaVesAs average global temperatures increase, we are likely to seemore record highs, and fewer record lows. This would makeheatwaves longer, more frequent and more intense.


Average Summer Temperature Switzerland (day & night), 1864 - 2003

Temperature (C)

10 12 14 16 18 20 22 24 26

2003

2002

1923

Source: Schr, C. et al. (2004) The role of increas-ing temperature variability in European summerheatwaves, Nature 427, 332-336.

heatwaVes

19

exprDr er friac, Zur

Climate extremes;heatwaves & health;

recent [email protected]

+41 44 632 82 41 Gmt +1

Dr l axndrccRc, aur

Extreme events; observa-tions; climate models

[email protected] +10

Pr. KrnhyUnvry in, Usa

Impacts; climate models

[email protected]

+1 806 742 0015 Gmt -6

Dr Jrry mNcaR, Usa

Climate variability; model-ling; climate extremes

[email protected]

+1 303 497 1331 Gmt -7

side normal extremes (see graphic below). Theycaused approximately 70,00043-45 and 55,00046

deaths respectively.47 Because almost everythinghas adapted to, or been made to withstand nor-mal historic extremes, the majority of impacts

are harmful outside this range.48,49 Keep in mindthough, that not all recent (and future) heatwaves

are outside of what would be expected.50

fuur prjn

Heatwaves are very likely to become generallylonger, hotter, and more frequent in places that

already experience them.51-53 In Europe, heat-waves such as 2003s could become five-to-ten

times more likely over the next 40 years.54,55 Onestudy suggests that by 2300, with an eventualglobal warming of 10C (possible under business-as-usual scenarios), heat and humidity wouldmake almost half of the worlds most populous

areas uninhabitable.56,57

Little research has focused on future impacts ofheatwaves on poorer areas; but with little capacity

to adapt,58

they will likely be severe.59

Areas lessused to heatwaves are likely to be ill-prepared. 60Cities will be more severely affected than ruralareas.61 The World Health Organisation (WHO) es-timates that every 1C increase in apparent tem-perature (heat and humidity together), leads to 3%

more deaths in European cities.62 Fewer deaths ingenerally milder winters will likely be outweighed(up to five times by 2100) by more deaths due toheatwaves.63,64

w p Yu n rbu v ng.65 Excessive heat can be caused by severalfactors, making heatwaves difficult to attribute

directly.66 However, warming caused by additionalgreenhouse gases has increased the likelihoodof

some heatwaves.67

hv r nur.68-70/ tr v bnv n p.71,72 Recent heatwaves inEurope (2003) and Russia (2010) were by far the

hottest of the last five centuries.73,74 Local tem-peratures are influenced by high-pressure sys-tems, promoted by natural atmosphere and ocean

circulations, or cycles such as ENSO.75 However,

climate change amplifies high temperatures, re-sulting in hotter, longer and more frequent heat

waves.76,77

i Urbn h ind (Uhi) .78 The UHIeffect can push already-high temperatures up fur-

ther in cities, intensifying heatwave conditions. 79It is not the cause of heatwaves. Death rates arealso higher in cities during a heatwave due to airpollution, making it seem as though the heatwave

is worse in urban areas.80,81

tr r d d np! 82,83 No-one issaying there will be no cold periods. But, as aver-age temperatures rise, we are likely to see morerecord highs and fewer record lows. This trend

is already evident in the USA84,85and Australia.86Peak temperatures are also rising much fasterthan the averages, making more extreme heat-

waves more likely.87

i br n rr bu d n-r k r pp n r ur.88,89As heatwaves get longer, hotter and more fre-

quent the number of additional people killed bythem will likely outweigh the reduction in deathsdue to fewer harsh winters (up to five times by

2100).90,91

w n yDr Kvn trnbr(National Center for Atmos-pheric Research, USA): For extreme events, thequestion isnt, Is it global warming or naturalvariability? It is always both. The question is just

how much each is contributing.92

Dr my an (Oxford University, UK): ... on amiddle-of-the-road scenario for emissions - as-suming we dont do very much to combat climatechange - temperature heatwaves as high as theone in 2003 would be occurring every other yearby the middle of this century, ... By the end of the

century, 2003 would be a cool year.93

Dr N Dnbug(Purdue University, USA):One might expect that an average warming offour degrees would equate to each day warmingby 4 degrees, but in fact the hottest days warm

quite a bit more.94

fr r n

crk wkvd n vbit.ly/heatwavesvideo

i xr dn ng?bit.ly/extremeevents

eurpn (2003) ndRun (2010)v urdbit.ly/2003and2010

i ngng xr?bit.ly/extremelyhot

w d y
http://www.pirc.info/factsheetsmailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/heatwavesvideohttp://bit.ly/extremeeventshttp://bit.ly/2003and2010http://bit.ly/extremelyhothttp://bit.ly/extremelyhothttp://bit.ly/2003and2010http://bit.ly/extremeeventshttp://bit.ly/heatwavesvideomailto:[email protected]:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


11/27

suryA warming climate does not mean the end ofcold or extreme winters.

Recent winters in the UK (and parts of theUSA) have been cold, but the temperature for

the entire Northern Hemisphere was warmerthan average.

In the UK, we could experience more coldwinters as the climate changes, though this isstill uncertain.

Globally, however, as temperatures rise, coldwinters are likely to be less severe, and lesscommon.

Snowfall may increase in some places as aresult of more evaporation in a warmer

climate.

cnxDuring the past few winters, the UK media ranstories with headlines ranging from Its so cold

that global warming cant be real,1-3 to cold and

snowy weather is caused by climate change. 4-6With or without this confusing media influence,it is likely that the cold winter had some impacton public belief in, or concern about, climate

change.7-9

Historically, the last few UK winters have onlybeen harsh relative to a period of quite mildones.10,11 The coldest UK winter12 of the last

century was 1962-63.13,14Parts of the sea were

frozen, as was the river Cam and parts of theThames;15,16over 400 league football matches

were postponed,17 with some pitches re-opening

as ice rinks.18 The second-coldest (and one of the

snowiest) was 1946-47:19 thousands of peoplewere cut off by snowdrifts up to seven metresdeep, and many villages relied on RAF helicoptersupplies; between January and March, snow fell

somewhere in the UK for 55 days straight.20

Bkgrund nClimate gives us an idea of what normal weathermight be at a given time of year, what the ex-tremes of weather look like, and how often theseextremes might occur. What is normal and ex-treme depends on the place. A cold and snowywinter here might be relatively common (and

more extreme) than you would expect in southernSpain, but less common (and less extreme) thanin Siberia - these places have their own climates.The global climate defines what is normal and ex-treme typically for the world as a whole, taking allthese places into account.

Cold and snowy weather will still occur in awarmer climate.21 This does not stop, cancel outor disprove the long-term warming of the globalclimate, but neither does it mean that cold or

snowy weather is caused by climate change.22

There are two main reasons for this:

1. What happens locally in the UK is not repre-sentative of what is happening globally (seegraphic below). Even though the winter of 2009-

10 was the coldest in the UK for over 30 years,i nthe Northern Hemisphere it was the fifth warm-

est winter on record.23,24 At the same time, itwas the hottest Southern Hemisphere summerever recorded.

2. Weather varies so much and so quickly thatany one extreme weather event cannot tell usmuch, if anything, about climate. Roughly 30years of weather gives us enough informationto define what the climate of a region, or theglobe, might be. Similarly, we need long peri-ods to see if what is normal or extreme haschanged. Changes over a few months (a coldand snowy winter) tell us very little about whatis happening to the climate.

Natural cycles have been responsible for cold

and snowy winters in the past, and will producemore in the future.25-27 Research suggests that asthe average temperature increases, cold wintersshould become less severe and less common

globally.28 Local, more immediate impacts onweather in the UK and USA are uncertain.29

cd p nd ng

Cold spells in the UK are caused mainly by naturalatmospheric cycles - the North Atlantic Oscilla-tion (NAO) and Arctic Oscillation (AO), which canbe seen as slightly different regional outputs of

the same process.30,31 In the negative phase ofboth, changes in air pressure around the Arc-tic (the jet stream) allow more cold air to travel

south,32 resulting in cold weather for parts of Eu-

rope, North America and Northern Asia.33,34

sNow & colDCold and snowy weather attracts media attention and can havean impact on public opinion and concern about a warmingworld, but it does not disprove climate change.


Global Surface Temperature Anomaly

-5.9 -4 -2 -1 -0.5 -0.2 +0.2 +0.5 +1 +2 +4 +6.4

Winter 2009-2010, December-February (+0.68C)

C

The differencebetween thewinter 2009-2010 averagetemperatureand the1951-1980average.

Source:NASAGISTEMP1.usa.gov/wintermap

sNow&colD

21

exprPr. mrk sundrUcl, UK

Winter storms;seasonal forecasting

[email protected]+44 (0)1483 204187 Gmt

Pr. mk lkdUnvry Rdng, UK

Solar activity; climatevariability; winter

[email protected]

+44 (0)118 378 5572 Gmt

Dr spn DrngUea, UK

Weather prediction;climate impacts

[email protected]

+44 (0)1603 592 533 Gmt

Dr J mrwr Undrgrund, Usa

Meteorology; weather;hurricanes

[email protected] -5

The sun may also make a minor contribution

to cold spells.35 Low solar activity could eithercontribute to changes in air pressure directly, orinfluence the cycles described above, though this

is not conclusive.36,37Cold winters in parts of theNorthern Hemisphere may even become more

common38

- the ongoing reduction of Arctic seaice could cause additional changes in atmospheric

circulation, 39-41 though scientific opinion is farfrom settled on this point.42

sn nd ng

Perhaps counter-intuitively,43 a warmer worldcould lead to more snow in some places.44,45 Morewarmth increases evaporation, which leads tomore moisture in the air and thus more precipita-tion.46 If it is sufficiently cold where or when thisprecipitation falls, it will fall as snow. 47 A warmerworld does not mean that there will be no coldplaces - if winter temperatures usually reach-6C, a warming of 2C will not stop it being coldenough to snow.48

w p i d/ nng, ng ppd/n r.49 Very cold or snowy weatheris short-term and local.50 It does not disprove cli-mate change. The long-term trend in global aver-

age temperature is upward.51,52

i un. The possible contribution of low solaractivity to cold winters has re-ignited this com-

mon sceptical argument.53

But, whereas the solaractivity cycle lasts roughly 11 years, the warming

trend is longer. On average over the last 35 years,the sun has cooled slightly, whilst temperatures

have risen (see, for instance, bit.ly/climatesun ).54

Gb rng du nur y, nun vy.55 Natural cycles do play a part inshort-term weather.56-58 However, they cannot ex-plain the long-term warming trend observed overthe last century.59,60 Only additional atmosphericCO2 arising from human activity explains the trendwe see (for more: bit.ly/notnaturalcycles , PDF].61

w n yRbr hnn(University Corporation for Atmos-pheric Research, USA): People across the north-ern hemisphere are facing the fact that a warmingplanet doesnt get rid of winter ... now is a goodtime to remind ourselves that weather, like deathand taxes, will always be with us.62

Dr Kvn trnbr(National Centre for Atmos-pheric Research, USA): Too many think globalwarming means ... relentless warming every-where year after year. It does not happen thatway.63

Dr J hnn(NASA, USA): The 48 statescover only 1.5 percent of the world area, so theU.S. temperature does not affect the global tem-perature much.64 (The UK covers only 0.05%.65)

Dr Pr s(Met Office, UK): The famouslycold winter of 1962/63 is now expected to occurabout once every 1,000 years or more, compared

with approximately every 100 to 200 years before1850.66 fr r n

wy d nr dn dprv ngbit.ly/reallygoodvideo

wnr 2009-10bit.ly/winter2009-10[PDF]

t xn ng dnd ny rbit.ly/warmsnow

wy up nr r s dbit.ly/whysocold

w d y
http://www.pirc.info/factsheetshttp://1.usa.gov/wintermaphttp://1.usa.gov/wintermaphttp://1.usa.gov/wintermapmailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/climatesunhttp://bit.ly/notnaturalcycleshttp://bit.ly/reallygoodvideohttp://bit.ly/winter2009-10http://bit.ly/winter2009-10http://bit.ly/warmsnowhttp://bit.ly/whysocoldmailto:[email protected]://1.usa.gov/wintermaphttp://bit.ly/whysocoldhttp://bit.ly/warmsnowhttp://bit.ly/winter2009-10http://bit.ly/reallygoodvideohttp://bit.ly/notnaturalcycleshttp://bit.ly/climatesunmailto:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


12/27

suryThe estimated rate of species extinction todayis 100-1,000 times higher than historicallynormal.

The actual number of recorded extinctions

is low; partly because we only know about asmall percentage of all species on Earth.

Climate change is not the main driver ofspecies extinctions either on land or in theoceans at present.

However, it is exacerbating problems thatalready threaten species and will likelyintroduce more threats to species in the

future.

cnxIn each of the five mass extinctions of the past,between 75-96% of all species became extinct.1The last, roughly 65 million years ago, wiped outthe dinosaurs.2 In each, it took up to 10 millionyears for species numbers to recover.3,4 All previ-ous mass extinctions are associated with abruptclimate changes (though with different causes). 5

The climate is changing faster than it was duringthe last mass extinction we are releasing CO2and acidifying oceans roughly ten times faster. 6,7

Other activities like deforestation and over-fishingalready threaten species.8 Changing land use andmore isolated ecosystems have made it harderfor species to adapt by moving.9 Though there isevidence of this happening in many places,10-14 forsome species climate may change too fast for them

to adapt. Climate change will likely contribute toa large number of species extinctions in the 21 stcentury,15,16 possibly becoming the main threat tospecies.17

Bkgrund nSince the year 1500, 869 species have become

extinct.18 This is very likely a significant underesti-mate because:

- Declaring a species extinct can take decades,and requires monitoring over large areas.19

- Scientists dont want to give up on a species tooearly, prematurely stopping conservation ef-

forts.20

- We only know about two million from a possible30 million species on Earth.21,22 Many specieshave likely been lost without us even knowingthey existed.

- Only 3% of those species identified have been

assessed for risk of extinction.23,24

- Small populations of a species can become

functionally extinct.25 Though unlikely to recover,they can take thousands of years to die out com-pletely.26

- Local extinctions dont count, even though they

can be a first step towards global extinction.27

Estimates of extinction are extrapolated to includespecies we dont know about, making rates of ex-tinction higher, but perhaps more realistic. Cur-rently, species are going extinct 100-1,000 timesfaster than normal; and the rate is increasing (seegraphic below).28

tr

Currently, habitat loss and invasive species arethe two main causes of extinction on land. Over-fishing is the main cause of local extinctions in

the oceans.29 It is not yet known whether climatechange has been the main factor in any speciesextinction. Often multiple threats act together.30The extinction of the Golden Toad, for example,has been linked to climate change, though other

threats also played a significant part.31

Species are threatened by changes in tempera-ture (land and ocean), precipitation, and extremesin both of these. Acidification (from absorbingatmospheric CO2), changes in salinity (from more/less precipitation near coastal areas) and anoxia(insufficient oxygen for life) additionally threaten

ocean species.32

Species most at risk from climate change are

likely to be living in:33

- Historically stable climates (e.g. the tropics).Species often cannot cope even with small

changes in climate.34

- Climates projected to change the most (e.g.the Arctic). Species cannot cope with too muchchange.

- Tight boundaries (up mountains, on islands or incoastal areas). These barriers mean that species

dont have anywhere to escape to.35

Climate change may have already contributed to

some species extinctions in these places.36

Prjn

The main causes of species extinctions will likelyremain the same for some decades. Climate

sPecies eXtiNctioNClimate change will likely make a bad situation worse for manyspecies, and could become the main cause of species extinctionin the future.


Distant past(fossil record)

Extinctionsperthousandspeciespermillenium

100 000

10 000

1 000

100

10

1

0.1

0

Recent past(known extinctions)

Future(modeled)

Projected futureextinction rate ismore than ten timeshigher than current rate

Current extinction rateis up to one thousandtimes highers than thefossil record

Long-term averageextinction rate

For every thousandmammal species, lessthan one went extinct

every millenium

Marinespecies

Source: MilleniumEcosystem Assessmentbit.ly/speciesmeaMammals Mammals Birds Amphibians All species

Rates of Species Extinction

eXtiNctioN

23

exprPr. ovhg-GudbrgGci, aur

Coral reefs; ocean acidifi-

cation; biodiversity

[email protected]

+61 07 3365 1156 Gmt +10

Pr. sur PDuk Unvry, Usa

Species extinctions; tropicalforests; biodiversity

[email protected]

+1 919 684 8741 Gmt -5

Pr. cr tUnvry Yrk, UK

Species impacts; habitatchange; evolution;conservation

[email protected]

+44 (0)1904 328646 Gmt

wndy fdniUcN, szrnd

Species vulnerability toclimate change; extinction

[email protected] +1

change will likely exacerbate the situation thecombination of threats will increase rates of ex-

tinction.37 It is difficult to project the exact threat

posed by climate change because: 38-40

- We dont know anything about many species,41

so we dont know if they can adapt.42

- We dont know the effects of species movement.Displaced species could become invasive spe-

cies, affecting native species.43

- The interactions between species (predatorand prey; competition for food and water), arecomplex. We cannot project how existing or new

(novel) ecosystems might work in the future.44,45

- Many different factors can contribute to speciesextinction it is difficult to project how they willall change.

Therefore, projected species extinction figuresshould be used only as a guide. Numbers varygreatly depending on the amount and type of spe-cies studied and the methods used from roughly

5% to almost 80%.46 All agree, however, that cli-

mate change will mean more extinction,47,48andcould become the main cause of extinctions over

the next 100 years.49

sp xnn & bdvry

Biodiversity includes all species, sub-species,populations, genetic differences within sub-species and populations, and the relationships

between them.50 If any one of these is lost, biodi-versity decreases. Extinction of a species requiresall its sub-species, populations and individualsto be lost. Biodiversity is lost faster than species

are.51-53 Global biodiversity has declined 30% since

the 1970s.54 Though it is difficult to disentanglethe impact of climate change from other causes

(as with species extinction),55 it is likely already a

large threat to global biodiversity.56,57

w p i n ng.58-60 Though climatechange is not yet a major driver of extinction, itexacerbates other threats and is likely already a

large threat to biodiversity.61,62Climate change isexpected to drive extinction rates up in the future,

potentially becoming the main cause.63

t nubr r xggrd 64/ rng65-67/ unrn.68 Extinction rates are estimates(see above).69 It is unlikely that they over-estimate

the problem, and more likely that they underesti-

mate it.70 All research agrees that extinction ratesare likely to increase over the next century, in part

due to climate change.71

wr r p uppdy gngxn?72,73 Recorded extinctions do not take intoaccount the millions of species we do not know

about, or havent assessed.74,75The number ofrecorded species extinctions is very likely a signifi-cant underestimate as a result.

exnn nur pr vun.76,77Spe-cies have, and always will go extinct. However, theestimated rate of extinction is currently 100 -1,000times what is normal, and will likely increase at

least in part due to climate change.78 Evolution of

new species is not balancing these losses. 79

Bu [ prur] p n rvrng(r vn rpprd r ug xn!), r n prb.80 Conservationefforts can change the trajectory of a species, de-creasing the likelihood of extinction. But very fewspecies thought extinct reappear, and those closeto extinction rarely recover fully.81 Cherry-pickingspecific species ignores the big picture the es-timated rate of extinction is currently 100-1,000

times what is normal, and is increasing.82

w n yPr. ax Rgr(International Programme on theState of the Ocean): Were seeing a combination ofsymptoms that have been associated with large,

past extinctions.83

Pr. sn sur(Species Survival Commission,International Union for the Conservation of Nature):There are uncertainties all the way down; theonly thing were certain about is the extent [ofextinction] is way beyond whats natural and its

getting worse.84

Pr. cr t(University of York, UK): Manyof the most severe impacts of climate change arelikely to stem from interactions between threats

rather than from climate acting in isolation. 85

Dr Ku tpr(United Nations EnvironmentProgramme): If one million species become ex-tinct... it is not just the plant and animal kingdomsand the beauty of the planet that will suffer. Bil-lions of people, especially in the developing world,

will suffer too as they rely on Nature for suchessential goods and services as food, shelter and

medicines.87fr r n

h ng pup rkbit.ly/speciesatrisk [PDF]

Drn p dby ngbit.ly/differentspecies [PDF]

s nbit.ly/oceandamage

w d y
http://www.pirc.info/factsheetshttp://bit.ly/speciesmeamailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://bit.ly/speciesatriskhttp://bit.ly/speciesatriskhttp://bit.ly/differentspecieshttp://bit.ly/differentspecieshttp://bit.ly/oceandamagehttp://bit.ly/oceandamagehttp://bit.ly/differentspecieshttp://bit.ly/speciesatriskhttp://bit.ly/speciesmeamailto:[email protected]:[email protected]:[email protected]:[email protected]://www.pirc.info/factsheets


13/27

suryNatural events associated with the start ofspring have occurred earlier over the last fewdecades.

Natural events associated with the start of

autumn are getting later, although this is lesspronounced.

Many independent lines of evidence confirmthis: studies on the ground, satellite data, andCO2 records.

The changes are not necessarily uniform:events for different species appear to changeat different rates. Not all species showsignificant change.

cnxThere is significant popular interest in the UKin the changing seasons. BBC TV programmesfocusing on seasonal events in the natural worldsuch as Springwatch andAutumnwatch are verypopular. The first series of Springwatch had

around four million viewers.1,2

Seasonal changes provide opportunities for widerpublic involvement in, and engagement with,scientific research. Approximately 40,000 peoplecurrently record the timings of natural events forNatures Calendar, a survey run by the Woodland

Trust since 1998.3 In the UK, personal involvementin this kind of research goes back to the 18 th cen-

tury.4 Several individuals have come forward with

long-term records. An 81-year-old woman fromSurrey was given an OBE in 2009 for her meticu-lous 62-year record of the leafing dates of trees

near her home.5

Bkgrund nThe study of the seasonal timing of natural eventsis called phenology. On land, and at higher lati-tudes, the seasons are most pronounced. Manystudies which assess seasonal changes focus onthe Northern Hemisphere, as two-thirds of the

worlds land is there.6,7 This leaves the Southern

Hemisphere less well-studied.8

Many studies only look at the phenological re-sponse to climate change in one or two specificspecies or populations of flora and fauna. Meta-analyses review hundreds of scientific papers,

encompassing tens of thousands of differentspecies, combining and comparing individualresults.9-12 The conclusions of these studies arethat the observed changes present a coherentpicture.13-16

sprng

Biological events associated with the start ofspring include the flowering of many plants, theemergence of hibernating species, the arrival ofmigrant birds and their egg-laying. Overall, theseevents have come earlier on average by nearlyfour days per decade in the UK and around two-to-three days per decade across the NorthernHemisphere.17,18

The degree of change varies enormously betweenspecies, partly because not all species use tem-perature to time

climate fact sheets pirc

Documents