9 CLIMATE AND POLLUTION

AIR:

9.3 How Do We Know the Climate is Changing

Faster than Usual

➢ Many scientists consider anthropogenic global climate change to be the most important environmental issue of our times.

➢ 1859 - John Tyndall measured the infrared absorption of various gases and described the greenhouse effect.

➢ 1895 - Svante Arrhenius predicted that CO2 released by coal burning could cause global warming.

MAUNA LOA OBSERVATORY➢ Established in 1957 (part

of an Int’l Geophysical Year)

➢ Intended to provide data on air chemistry in remote, pristine environment

➢ Where the first evidence of increasing atmospheric CO2 due to human activities came from

FIGURE 1: Measurements of atmospheric CO2 taken at the top of Mauna Loa, Hawaii show an increase of 1.5-2.5 % each year in recent years. For CO2, monthly mean (red) and annual mean (black) CO2 are shown.

Temperature represents 5-year anomalies.

Scientific consensus is clear➢ Climate scientists worldwide have collaborated in

collecting and sharing data and in programming models to describe how the climate system works.

➢ The evidence shows unequivocally, as in the Mauna Loa graph, that climate is changing and the global average is warming because of increased retention of energy in the lower atmosphere.

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC)➢ Most comprehensive effort to

describe that state of climate knowledge

➢ A collaboration among governments, with scientists and government representatives from 130 countries

➢ Aim: to review scientific evidence on the causes and likely effects of human-caused climate change.

➢ 2007 - IPCC issued its Fourth Assessment Report○ Four volumes of the report represent a

consensus by more than 90% of all the scientists working on climate change.

○ Conclusion: 90% certainty that observed climate change is caused by human activity

Changes in heat waves, sea level, and storms are expected

➢ The Fourth Assessment Report presents a variety of climate scenarios for predicted emissions of greenhouse gases.

➢ Scenarios differed in expected population growth, economic growth, energy conservation and efficiency and adoption of greenhouse gas controls.

➢ About 2-4°C (about 3-8°F) - “best estimate” for temperature rise now according to IPCC

➢ Observations since 2007 show that all the IPCC scenarios were too conservative.

➢ Greenhouse gas emissions, temperatures, sea level and energy use have accelerated faster than projected by any of the IPCC projections.

➢ There is a serious concern that increased heat stress and drought could cause increased deaths as well as crop failure and new waves of refugees from drought-stricken regions.

FIGURE 2: Emissions scenarios and actual emissions observed after

scenarios were modelled.

“Climate change, national security, and energy dependence are a related set of global challenges that will lead to tensions even in stable regions of the world.”- US Military Advisory Board, 2007➢ The United States Military is concerned about global

warming.➢ Some international aid agencies point to the civil war and

accompanying humanitarian crisis in the Darfur region of Sudan.○ These problems are rooted in drought and food

shortages caused by changing weather patterns that have led to years of below normal rainfall and desertification.

➢ Climate scientists point out that shifting our energy strategy from coal to wind, solar and greater efficiency could produce millions of new jobs and save billions in health care costs associated with coal burning.

➢ Since preindustrial times, atmospheric conditions of CO2, methane (CH4) and nitrous oxide (N2O) have climbed by over 31%, 151% and 17% respectively.

The main greenhouse gases are CO2, CH4, and N2O

Carbon Dioxide (CO2) - most important because of its abundance and lasts for decades for centuries in the atmosphere.

➢ Fossil fuel use - 80% of CO2 emissions○ Other sources - cement production and burning of

forests and grasslands○ 33 billion tons every year by average

Methane (CH4) - much less abundant than CO2 but absorbs 23 times as much as infrared energy per molecule and is accumulating in the atmosphere about twice as fast as CO2

➢ Produced anywhere organic matter decays without oxygen, especially under water

➢ Natural gas➢ Released by ruminant animals,wetrice paddies, coal

mines, landfills, wetlands and pipeline leaks➢ Reservoirs for hydroelectricity - important source of

CH4 because they capture submerged, decayed vegetation

Nitrous Oxide (N2O) - produced mainly by chem.reactions between atmospheric N and O

➢ Other sources: burning of organic material and soil microbial activity

Chlorofluorocarbons (CFCs) and other gases containing Fluorine - store heat from infrared energy

FIGURE 3: Contributions to global warming (a) by different gases and activities, (b) by different countries

Evidences of climate change is overwhelming

“As best as can be determined, the world is now warmer than it has been in any point in the last two millennia and if current trends continues, by the end of the century it will likely be hotter than at any point in the last two million years.”- American Geophysical Union➢ American Geophysical Union is one of the nation’s

largest and most respected scientific organizations.

Some of the evidences that led AGU to their conclusion:1. Over the last century, the average global temperature has

climbed about 0.6°C (1°F).2. Polar regions have warmed much faster than the rest of

the world.3. Arctic sea ice is only half as thick now as it was 30 years

ago, and the area covered by summer sea ice has decreased by about half in just three decades.

4. Ice shelves on the Antarctic Peninsula are breaking up and disappearing rapidly.

5. Nearly all alpine glaciers are retreating rapidly.

6. So far, the oceans have been buffering the effects of our greenhouse emissions both by absorbing CO2 directly and by storing heat.7. Sea level has risen worldwide approximately 15-20cm (6-8 in) in the past century.8. Satellite images and surface measurements show that growing seasons are now as much as three weeks longer in a band across northern Eurasia and North America than they were 30 years ago.9. Droughts are becoming more frequent and widespread.10. Biologists report that plants and animals are breeding earlier or extending their range into new territory.

11. Coral reefs worldwide as “bleaching” as water temperatures rise above 30°C (85°F).12. Storms are becoming stronger and more damaging.

Controlling emissions is cheap compared to climate change➢ 2010 study by Pew Trust - evaluated estimates of the cost of

lost ecological services by 2100○ Costs included factors such as:

■ Lost agricultural productivity from drought■ Damage to infrastructure from flooding and storms■ Lost biological productivity■ Health costs from heat stress■ Lost water supplies

Sir Nicholas Stern - estimated the immediate costs of climate change would be at least 5% of the global GDP each year (British gov’t)

➢ For many people, global climate change is a moral and practical issue as well as a practical one.

➢ Religious leaders are joining with scientists and business leader to campaign for measures to reduce greenhouse gas.

➢ Scientific studies have long been unanimous about the direction of climate trends but commentators on television, newspapers and radio continue to fiercely dispute the evidence.

➢ Climate scientists offer the following responses to some of the claims in the popular media:

1. Reducing climate change requires abandoning our current way of life.

2. There is no alternative to current energy systems.3. A comfortably lifestyle requires high CO2 output.

Why are there disputes over climate change?

4. Natural changes such as solar variation can explain observed warming. 5. The climate has changed before, so this is nothing new.6. Temperature changes are leveling off.7. We had cool temperatures and snowstorms last year, not heat and drought.8. Climate scientists don’t know everything, and they have made errors and misstatements.

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