chapter 21: global climate change. foreword the issue of global climate change may be one of the...

Chapter 21: Global Climate Change

Foreword

The issue of global climate change may be one of the most important issues facing humanity in its historyThis issue has the potential to affect the economies, safety and health of the entire world’s populationHopefully you’ll understand after this review why the science of this topic is so difficult to understand and why it generates so much political controversy

The Earth’s climate system consists of complex interactions between many components!

The Earth Systems Science Approach recognizes five natural subsystems: atmosphere, hydrosphere, geospherebiosphere and heliosphere. Most researchers now recognize a sixth, non-natural subsystem: the anthroposphere.

Global Climate Change

We’ll focus on some basics of the climate system such as atmospheric chemistry and the greenhouse effect

Sun

About 30% of incomingsolar energy reflected back to space

radi

ated

hea

t

Greenhouse gases absorb radiated heat andreradiate some of it to the lower atmosphere

Earth materials and atmosphere absorb about 70% of incoming light energy; some portion of this energy isemitted to the atmosphere as radiated heat

Greenhouse Effect – gradualwarming of the Earth’s loweratmosphere and surface whencertain gases (e.g., H2O, CO2 andCH4 ) absorb heat radiated from theEarth’s surface and then reradiateportions of it

Earth’s AtmosphericComposition (Dry Air)

Greenhouse Effect

Would the average person view the greenhouse effect as beneficial or detrimental?Most people erroneously think that the greenhouse effect is detrimental; the greenhouse effect is a natural phenomenon that helps modify the Earth’s climate and produce livable biological niches

Greenhouse Effect

Atmospheric scientists suggest the Earth’s average surface temperature would be about 60 - 70 degrees F colder without a greenhouse effect; under these conditions most of the Earth’s surface would host Arctic conditions - the flora and fauna of Earth would be drastically reduced in number and diversity

Global Warming EvidenceThere is firm evidence that the greenhouse effect is being enhanced and that we are entering a global warming periodThis evidence includes: 30 of the highest world average annual temperatures ever recorded (since 1880) recorded from 1976-2014; with the exception of 1998, the nine hottest years have occurred since 2001 (2014 was the hottest global year on record, 2005 and 2010 the second hottest);about a 50% reduction in European Alps glacier ice in the last 100 years; Source: National Geographic, Sept. 2012

an average rise in world sea levels of about 1 foot during the last century; a decline of about 42% in Arctic sea ice volume in the last 30 years; and the quick melting of portions of the Greenland and Antarctic ice sheets and Antarctic ice shelves (1995, 2002 and 2008 – in March 2002 a portion of the Larsen ice shelf the size of Rhode Island (1250 mi2 ) collapsed into the Antarctic Ocean) (see slides)

Change in Arctic Sea Ice Minimum 1979-2007

Global Warming Evidence

Global Warming Evidence

Global Warming

The accumulating evidence suggests global warming is occurring but whether natural or human forces (or both) were causing climate change was vigorously debatedHowever, the debate in the scientific community has mostly ceased

Global WarmingThe IPCC (Intergovernmental Panel on Climate Change – consisting of more than 1500 scientists from about 60 nations) released a paper in February 2001 contending the evidence was significant to support that human actions are modifying the climateFurthermore: a November, 2004 report published by 250 scientists from eight nations indicates that the Arctic is warming twice as fast as the rest of the globe – in their opinion likely the consequence of increased atmospheric levels of greenhouse gases due to increased fossil fuel combustion by humans

Global Warming

However, note in the adjacent article research suggesting natural causes for an ancient warming trend

Global Climate Change

The 2013 IPCC (Intergovernmental Panel on Climate Change) report contends that human actions are significantly driving climate change (95% confidence level)

Global Warming

Global Climate Research

In simple models, the more greenhouse gases in the atmosphere the more radiated heat from the surface gets trapped and the higher the atmospheric and surface temperaturesWhat are some natural sources of greenhouse gases?

Greenhouse Gas SourcesWhat are some other natural sources of greenhouse gases? Are these sources easy to accurately quantify on a worldwide basis?Is this a simple or complex research topic?

Climate Reconstruction Research

Ice sheet core samples (see figure) and other materials are being ingeniously investigated for their ability to retain indications of prior atmospheric chemistry and temperatureScientists are attempting to detail ancient atmosphere greenhouse gas levels to see if they’ve ever fluctuated as much naturally as they’ve done in the last 56 years

Global Warming

Although reconstruction of ancient atmospheric chemistries and climates from ice cores suggest that air CO2 levels haven’t been higher than currently in the last 800,000 years (IPCC – 2014), some data suggest CO2 levels have naturally fluctuated much more than within the last 160 years (millions of years ago). (see figure)

Industrial Revolution


In addition, we are still learning about other sources of greenhouse gases and can’t be sure that we’ve quantified their releases accurately (see figure)

Possible Global Climate Change Outcomes

If atmospheric greenhouse gas concentrations continue to rise and enhance the greenhouse effect, what are some of the proposed consequences of global warming?Remember: although the topic discussed is often called “global warming” the entire globe won’t be affected similarly, subsequently many researchers and politicians now employ the phrase, “global climate change”


Consequences could include: 1) significant rises in sea levels as increased glacial ice melting occurs; the rising waters could permanently displace millions of people (see figures);

National Geographic: August, 2007


Note the adjacent examples of the threat of rising seas

2) Reduction of tillable land as sea levels rise;


3) Changes in world weather patterns and a higher frequency of severe weather events (e.g., hurricanes, severe thunderstorms, blizzards, extended heat waves, droughts);

North Atlantic Tropical Storm Frequency

National Geographic: August, 2007


Source: National Geographic, Sept. 2012

1980 - 1995: 46 US weather disasters with at least $1 billion in damages

1996 - 2011: 87 US weather disasters with at least $1 billion in damages

Source: US National ClimaticData Center

2012 Superstorm Sandy


Global climate change will have local impacts!


4) A greater percentage of land becomes arid and less productive; the glacial source of some major rivers (e.g., the Ganges) may be reduced or eliminated long term (a few hundred years)


5) The biodiversity of coastal ecosystems declines due to an inability to adapt quickly to rising, warming and acidifying seas (e.g., reefs);

CNN.com 3/31/06

Bleached coral


6) Diseases spread by flies, mosquitoes, ticks become more prevalent as the warmer climates produce longer and more intense infection periods (think about the rapid spread of West Nile Virus across the U.S.); and

1/26/2012

Warm, less salty surface current

Cold, salty deep current

Gulf Stream:50-90 miles wide;maximum discharge:540 billion tons/hour

7) The deep-water return flow of the Gulf Stream current is reduced/eliminated leading to much colder conditions in the North Atlantic (see figure)

Possible Global Climate Change OutcomesMost climate scientists think there is enough evidence of these effects occurring to strongly support that global climate change is occurring at a rate that requires worldwide action Complicating factors: How would climate change influence the Jet Stream or weather patterns generated during El Nino and La Nina events?


Please remember that the seven categories of global climate change outcomes we discussed are projections, not a guaranteed reality - the projections are based on incomplete data and an incomplete mathematical understanding of the Earth’s dynamic processesThe first global warming computer models treated the Earth as a rocky ball devoid of life - simpler to model mathematically!

Variables Affecting the Degree of Climate ChangeThere are other variables (factors) which may affect the degree of climate change.1) A few scientists have proposed that as air CO2 levels rise, plant productivity will rise since CO2 is necessary for photosynthesis; the more CO2 absorbed by plants the less likely a severe global warming event

Variables Affecting the Degree of Climate ChangeExperiments with plants in CO2-enriched lab atmospheres and outside forest plots have produced variable results - hardwood trees respond positively and absorb more CO2 for a few years; most grasses and ferns show declines in productivityTherefore could the distribution, and type, of plant species (and animals) across the globe be altered? (see figure)

Source: NationalGeographic, June, 2008

Variables Affecting the Degree of Climate ChangeA nutrient (iron) seeding project in a portion of the southern Pacific ocean in 1993 successfully increased the population of CO2-absorbing phytoplankton, however the positive results were short-livedDo you advocate “geoengineering” on a large scale? (see slide)A Californian company, Climos, wants to commercialize iron fertilization and an India/Germany iron fertilization experiment was completed in 2009

GeoengineeringNote the India/Germany iron fertilization experiment was not very successful

Earth Magazine, June 2009

Source: Earth Magazine; December 2008

Geoengineering

Pay attention to this topic!

Variables Affecting the Degree of Climate Change

In addition, fairly recent (2004) data from the TERRA satellite suggests plant productivity has increased 5-10% on average worldwide during the last twenty yearsHow would this hypothesis be affected by continued deforestation and land development?

EarthSky // Earth, Science WireRelease Date: May 31, 2013•145•

Increasing CO2 in air is making deserts greenerScientists call this a “carbon dioxide fertilization effect.” It has caused a gradual greening of arid regions on Earth from 1982 to 2010.Scientists have long suspected that a flourishing of green foliage around the globe, observed since the early 1980s in satellite data, springs at least in part from the increasing concentration of carbon dioxide in Earth’s atmosphere. Now, a study of arid regions around the globe finds that a carbon dioxide fertilization effect has, indeed, caused a gradual greening from 1982 to 2010. View Larger | New research links gradual greening of arid areas like Australia’s outback to increasing concentrations of atmospheric carbon dioxide. Photo by Bruce DoranFocusing on the southwestern corner of North America, Australia’s outback, the Middle East, and some parts of Africa, Randall Donohue of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Canberra, Australia and his colleagues developed and applied a mathematical model to predict the extent of the carbon-dioxide (CO2) fertilization effect. They then tested this prediction by studying satellite imagery and teasing out the influence of carbon dioxide on greening from other factors such as precipitation, air temperature, the amount of light, and land-use changes.The team’s model predicted that foliage would increase by some 5 to 10 percent given the 14 percent increase in atmospheric CO2 concentration during the study period. The satellite data agreed, showing an 11 percent increase in foliage after adjusting the data for precipitation, yielding “strong support for our hypothesis,” the team reports.

Update

Variables Affecting the Degree of Climate Change2) Some scientists have proposed the world’s oceans could absorb enough air CO2 to offset a significant global warming event; investigations are being conducted to test this hypothesis


Preliminary results (2003) suggest the oceans absorb more carbon than they emit – about 2 billion tons annuallyPotential problems: a) warm waters absorb less carbon dioxide; if the oceans continue to warm this carbon dioxide “sink” will decrease (see article);b) increased carbon dioxide absorption by the ocean will decrease the pH (make more acidic) of the ocean’s waters and threaten to dissolve the exoskeletons of reef corals and certain shellfish (see slide)

CNN.com; 5/18/2007

5/28/08


Oceans’ acidic shift may be fastest in 300 million years


Variables Affecting the Degree of Climate Change3) Multiple hypotheses exist involving clouds: warming will result in more atmospheric water vapor; some climatologists suggest this will result in more high-elevation cloudsA 4% increase in high-elevation clouds could cause enough sunlight to be reflected (off cloud ice crystals) back to space to offset a significant global warming event (see figure)

Source: National Geographic, Sept. 2012

icecrystals

icecrystals

high-altitude clouds

reflected sunlight

Variables Affecting the Degree of Climate Change4) Other modelers suggest that if any additional clouds form at low altitudes (these lack many ice crystals) that they would spur a significant global warming event since water vapor is an effective greenhouse gas (see figure)These are only a few of the future climate models - this field of study is very complex!

no icecrystals

no icecrystals

low-altitude clouds

Radiatedheat

Was a greater concentration of low-elevation clouds responsible for the atypically high glacial melt rates in Greenland in 2012?


chapter 21: global climate change. foreword the issue of global climate change may be one of the...

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global warming evidenceglobal

antarctic ice sheets

antarctic ice shelves

hottest global year

arctic sea ice minimum

arctic sea ice volume

earths loweratmosphere