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LUMCON Gulf Lagniappe Adult Education Workshop Series:Climate Change

Intergovernmental Panel on Climate Change (http://www.ipcc.ch/)--4th Assessment Report

Dr. Brian Roberts, Assistant Professor, LUMCON

The Earth’s climate has changed

dramatically over time

Climatic changes in the gdistant past were driven by natural causes, such as

variations in the earth’s orbit, variations in solar intensity, and

carbon dioxide content of the atmosphere

The Earth’s climate has changed

dramatically over time

Climatic changes in the gdistant past were driven by natural causes, such as

variations in the earth’s orbit, variations in solar intensity, and

carbon dioxide content of the atmosphere

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Definitions of climate change

•Climate change in IPCC usage refers to a change in the state of the climate that can be identified (e.g. using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. It refers to any change in climate over time, whether due to natural any change in climate over time, whether due to natural variability or as a result of human activity.

•This usage differs from that in the United Nations Framework Convention on Climate Change (UNFCCC), where climate change refers to a change of climate that isattributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods.

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level”

•11 of the last 12 years rank among the 12 warmest recorded (since 1850)

•100-year linear trend (1906-2005) of temperature increase is 0.74ºC

IPCC AR4

•Global sea level has risen since 1961 at an average rate of 1.8 mm/yr and since 1993 at 3.1 mm/yr

•Satellite data since 1978 show that annual average Arctic sea ice extent has shrunk by 2.7% per decade, with larger decreases in summer of 7.4% per decade

Planetary Anthropogenic Effects• The best-known way humans inadvertently modify climate is

by enhancing the natural capacity of the atmosphere to trap radiant heat near the Earth's surface--the so-called greenhouse effect.

• This natural phenomenon allows solar energy to reach the Earth's surface and warm the climate. Gases such as water vapor and CO2, however, trap a much larger fraction of long wavelength radiant energy called terrestrial infrared radiation near the Earth's surface. This causes the “greenhouse effect” to be responsible for some 33°C (60°F) of surface warming. Thus, seemingly small human-induced changes to the natural greenhouse effect are typically projected to result in a global warming of 1°C to 5°C in the next century.

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Climate Change - Global Energy BalanceIncoming Solar Radiation

30% reflected fback into

space

Climate Change - Global Energy Balance

Greenhouse gases

What causes the problem?• Basically, human economic development has

changed our physical and chemical environment in ways that modify natural resources and natural cycles (i.e. global carbon cycle).

• Burning fossil fuels that release CO2 or using land for agriculture or urbanization that cause deforestation contribute to the problem.

• When these become large enough, significant global (worldwide) changes are expected.

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2008 was the 50th anniversary of the initiation of a continuous CO2 record at Mauna Loa, Hawaii by Charles Keeling

Feb 2011: 391.76 ppmv

Plot scale(chamber measurements)

Ecosystem scale(eddy flux measurements)

Changes in Greenhouse gases from ice cores and modern data

Global atmospheric concentrations of CO2, CH4, and N2O increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values spanning many thousands of years

•Annual CO growth rate larger from 1995•Annual CO2 growth rate larger from 1995-2005 (1.9 ppm per year) than the beginning of continuous record (1.4 ppm per year)

•Global CH4 concentration increased from pre-industrial value of 715ppb to 1774ppb in 2005.

•Global N2O concentration increased from 270ppb to 319ppb in 2005.

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Global GHG emissions due to human activities have grown from pre-industrial times, with an increase of 70% between

1970 and 2004

Figure 2.1. (a) Global annual emissions of anthropogenic GHGs from 1970 to 2004.5 (b) Share of different anthropogenic GHGs in total emissions in 2004 in terms of CO2-eq. (c) Share of different sectors in total anthropogenic GHG emissions in 2004 in terms of CO2-eq. (Forestry includes deforestation.)

•US responsible for > ¼of cumulative CO2 emissions since 1750

Chi ts f •China accounts for second highest total (8.4%) but is the fastest growing contributor

Monastersky 2009 Nature

Radiative forcing is a measure of the influence a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism. In the IPCC report, radiative forcing values are for changes relative to preindustrial conditions defined at 1750.

Natural source contribution to radiative forcing since 1750 very small

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Most of the observed increase in global average T since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations (IPCC AR4)

•Significant anthropogenic warming over each continent over the past 50 years

•Temperature increase is widespread over the globe and is greater in northern latitudes

•Land regions have warmed faster than the oceans

•Between 1955 and 1998, 84 % of the total increase in heat content of the earth system went into the ocean

the majority of the heat increase has gone into the ocean

went into the ocean

•Without this vast reservoir for heat storage, the continents and atmosphere would be much warmer

Blue - 1961-2003Purple - 1993-2003

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As a result of this large input of heat energy, the oceans have measurably warmed

60S–60N geographicallyaveraged ocean temperature anomalies down to 500 m, from 1950 until 1998.

Temperature increase is not uniform

These are atmospheric temperatures but ocean temperatures show the same pattern

Temperature increases in the ocean can also lead to change in stratification

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•increased stratification associated with i l l li k d t d i NPP

Global analysis

warming was closely linked to decreasing NPP•the opposite pattern in higher latitude waters was not observed

(Behrenfeld et al 2006)

the future under continued warming ?? ‘waters containing < 0.07 mg L-1 chl have expanded 15 % (6.6 million km2 in 9 years)’

(Polovina 2008)

It has been proposed that continued warming of ocean water temperatures might lead to a disruption in thermohaline circulation, possibly resulting in a dramatic decrease in

temperatures in Europe

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In the high-latitude regions in both hemispheres, the surface waters show an overall freshening consistent with these

regions having greater precipitation, although higher runoff, ice melting,

Widespread evidence for changes in ocean salinity at gyre and basin scales in the past half century

•near-surface waters in the more evaporative regions increasing in salinity in almost all ocean basins

•Salinity changes imply changes are occurring in the hydrological cycle over the oceans.

although higher runoff, ice melting, advection and changes in the meridional

overturning circulation may also contribute. The subtropical latitudes in both

hemispheres are characterised by an increase in salinity in the upper 500 m. The patterns are consistent with a change in the

Earth’s hydrological cycle, in particular with changes in precipitation and inferred larger water transport in the atmosphere from low latitudes to high latitudes and

from the Atlantic to the Pacific.

IPCC (2007)

Stratification can also increase via a decrease in salinity (freshening of surface)

Western North Pacific

30 year time series:

Surface salinity decreaseStratification increase

Stratification set up earlier Vertical mixing reducedVertical mixing reduced

(from Chiba et al. 2004)

Phytoplankton production: winter – increasedspring (diatoms) – reduced summer (small phyto) – increased

Zooplanktondecreased overall

Stratification, phenology, and ecosystem composition

all changed in system

Eastern North Pacific - permanent halocline

Freeland and Cummings (2005)

How might this shoaling of the mixed layer effect primary production?

[Fe] in ML would increase b/c the same dust inputs of Fe would occur in a smaller volume of water (shallower ML) increased PP b/c diatoms are Fe-limited (also expect increased drawdown of macronutrients b/c upwelling reduced)

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2010: 389.78 ppm

About 40 % of anthropogenic CO2 has been dissolved in the

CO2 in the ocean is

increasing

Without this, atmospheric CO2

concentrations would be higher! (and

atmospheric warming would be greater)

ocean.

Increase in Oceanic CO2 = Oceanic acidification

When CO2 enters the ocean, carbonic acid is formed:CO2 + H2O = H2CO3

This dissociates to: H2CO3 = H+ + HCO3-

Further/some: H+ + CO3-2 = HCO3

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Th ddi CO t t

•Since pre-industrial times, the average surface pH of the ocean has decreased by 0.1 (~30% increase in H+ ions)•By 2100, ocean pH will become another 0.3-0.4 units lower (~100-150% inc in H+)

•Since organisms & ecosystems are adapted to a narrow range of pH, this raises extinction concerns, directly driven by inc. atmospheric CO2, that could disrupt food webs & impact human societies that depend on marine ecosystem services

Thus, adding CO2 to seawater:- makes it more acidic (H+)- reduces carbonate ions, making it harder for CaCO3 to form

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Two important groups of CaCO3 (calcite) based unicellular plankton

Foraminifera (dots are symbiotic algae) Coccolithophores: Emiliania huxleyi

Emiliania huxleyi blooms

Coccolithophore blooms are commonly seen in sub-tropical and temperate seas, and increasingly commonly in higher latitudes

•can be an important component of the phytoplankton

Eastern Bering SeaNewfoundland

In the North Pacific, hi li (1) i h li

Greater than ‘1’ above this depth

CaCO3 Saturation state:> 1 - formation of shells and skeletons can occur< 1 - seawater is corrosive and dissolution begins (unless protective mechanisms exist).

this line (1) is shoaling at about 1-2 m yr-1.

In some upwelling areas, the ‘1’ depth now overlaps with some important calcareous based plankton.

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Natural experiment on ecosystem effects of ocean acidification: volcanic carbon dioxide vents

Hall-Spencer et al. (2008) Nature

Calanus finmarchicus biomass in North Sea

Are organisms moving in response to climate change?

Between 1960s and 1990s, total Calanus biomass has declined by 70%. This huge reduction in biomass has had important consequences for other marine wildlife in the North Sea especially fish larvae (e.g. cod larvae).

High recruitment

Low recruitment

Warm temperate species

Temperate species

Latitude Shifts – NE Atlantic

Subarctic species

Arctic species

(from Beaugrand et al. 2002)

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Sea Birds On an island off the coast of Scotland, there are more than 1,200 guillemot nests. In spring (2004), all of them were empty.

24,000 nests of another seabird, the arctic tern, were almost entirely empty.

the adult birds were starving. They eat sand eels but the sand eels had disappeared

Some species can’t shift

eels but the sand eels had disappeared…….

Sand eel

•Because the cold-water plankton that they eat had migrated north…..•Because the waters between Scotland and Scandinavia had become too warm.

Why?

Abyssal ecosystems (ocean floor depths of 3000-6000m) cover 54% of the Earth’s surface

•network of plains and rolling hills punctured by seamounts, and subdivided by mid-ocean ridges, island arcs and ocean trenches

Smith et al. (2008)

Smith et al. (2008)

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Abyssal ecosystems “fueled” by POC flux from euphotic zone↑CO2 ↑SST ↑Stratification (shallower mixed layer) ↓Nutrient upwelling shift from diatom/large

zooplankton assembage to picoplankton/microzooplankton assemblage ↓ ↓POC flux to abyssal zone

Overall, climate change is predicted over the

next century to significantly reduce

marine export production and POC

Smith et al. (2008)

production and POC flux to the deep ocean,

enhancing stress in already food-poor

abyssal ecosystems.

Arctic food web:ice algae - amphipods – cod – seals - polar bears

Ecosystem restructuringHigh latitude ice communities

The worldwide population: 10,000 - 20,000.

Adult males: 550 - 1,700 lbs; 8 to 10 feet long Adult females: 200 - 700 lbs, 6 - 8 feet long

Small and helpless at birth - average 1.3 lbs Cubs stay with mother for about 2.5 years

•Main food source: ringed seals, bearded seals.

•Polar bears depend on a frozen platform from which to hunt seals. Without ice, the bears are unable to catch seals.

Sea ice is melting earlier in the spring and forming later in the autumn.

In Hudson Bay, the main cause of death for cubs is either lack of food or lack of fat on nursing mothers.

For every week earlier the ice breaks up in Hudson Bay, bears come ashore roughly 10 kg (22 lbs) lighter and in poorer condition.

On average, today's Hudson Bay polar bear weigh about 200 lbs less than it did 15 years ago

Hudson Bay bears – (southern part of their range)

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Arctic bears

Arctic sea ice has declined (blue line) and in Alaska bears are increasingly spending

summer on land

2010 was the tenth consecutive year September sea ice extent has been below the long-term (1978-2000) mean

Polar bears??

The Polar Bear is an indicator of larger changes in the entire ecosystem – it is not changing in isolation.

All ice-dependent animals are adversely affected by warming in the Arctic.

•Ringed seals need the ice as a place to birth pups. •Arctic cod a major prey for seals live in ice cracks Arctic cod, a major prey for seals, live in ice cracks. •Ice algae need ice as a surface on which to grow. •Different zooplankton feed on ice algae vs algae in

open water

As the ice disappears, the whole ecosystem changes

Examples of impacts associated with global average temperature change(impacts will vary by extent of adaptation, rate of temperature change & socio-economic pathway)

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Conclusions thus farThere are many ways climate change is affecting and will affect the ocean

Most cannot be quantitatively predicted because of non linearities in biological systems ecosystems non-linearities in biological systems - ecosystems are complex

Neither temperature nor CO2 in the ocean are at equilibrium with the atmosphere so the ocean will continue to become more acidic and warmer for some time – even if there are no further emissions.

However: emissions continue to increase

Scenarios for Global GHG emissions from 2000 to 2100 in the absence of additional climate policies

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Also: temperature increase is accelerating

“Continued greenhouse gas emissions at or above current rates will cause further warming and induce many changes during the 21st

century that are very likely (> 90 %) to be larger than those observed during the 20th century” (from the 4th IPCC report, Feb 2007)

Atmosphere-Ocean General Circulation Model projections from three SRES scenarios of surface land and ocean

warming for early and late 21st century

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Relative changes in precipitation for the period 2090-2099 relative to 1980-1999

December – February June - August

•Precipitation increases in high-latitudes very likely•Precipitation decreases in most subtropical regions are likely

Large-scale relative changes in annual runoff for the period 2090-2099 relative to 1980-1999

Changes in precipitation and temperature lead to changes in runoff and water availability. Runoff is projected to increase 10-40% by mid-century at higher latitudes and in some wet tropical areas and decrease 10-30% over some dry regions at mid-latitudes and dry tropics, due to decreases in rainfall and higher evapotranspiration rates. Many semi-arid areas (e.g. western United States) will also suffer a decrease in water resources. Drought-affected areas are projected to increase in extent, with the potential for adverse impacts on multiple sectors, e.g. agriculture, water supply, energy production and health.

21st century regional changes•Warming expected to be greatest over land and at most high northern latitudes and least over the Southern Ocean and northern Atlantic (continuing recent trends)•Snow cover area is projected to contract. Increases in thaw depth will be widespread over most permafrost regions. Sea ice in both the Arctic and Antarctic will shrink (with Arctic late-summer sea ice almost entirely (with Arctic late summer sea ice almost entirely disappearing by late 21st century)•Very likely that hot extremes, heat waves, and heavy precipitation will become more frequent•Ongoing increases in SST will likely lead to future tropical cyclones (typhoons and hurricanes) becoming more intense with larger peak wind speeds and more heavy precipitation

•Less confidence in projections of global decrease in numbers of tropical cyclones