THE FAQS OF GLOBAL WARMINGBy Rachel Lewis and Philip Orton, GHN Volunteer Speakers SCIENCE: BASICS 1. What is the greenhouse effect? SCIENCE: TOUGH QUESTIONS, SIMPLE ANSWERS 9. Is Antarctica melting? ECONOMICS, POLITICS 14. What can we all do about global warming?
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| 1. WHAT IS THE GREENHOUSE EFFECT? | TOP |
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The "greenhouse effect" refers to the natural phenomenon that keeps the earth warm enough for life to flourish. The sun's enormous energy warms the earth's surface and its atmosphere. This energy radiates back toward space as heat, but a portion is retained by heat-trapping gases in the atmosphere - among them carbon dioxide and methane - which create an insulating layer. Without the temperature control of the greenhouse effect, the earth could not sustain life. As some people have put it: too much greenhouse gas, and Earth would be as hot as Venus; to little and we'd be cold as Mars.
| 2. WHAT IS GLOBAL WARMING? | TOP |
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"Global warming" refers to the rise in the earth's overall temperature resulting from an increase in heat-trapping gases in the atmosphere.
| 3. WHAT IS CAUSING GLOBAL WARMING? | TOP |
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Scientists have concluded that human activities are contributing to global warming by adding large amounts of heat-trapping gases to the atmosphere. Our use of fossil fuels - coal, oil and natural gas - is the main source of these emissions. Every time we drive a car, use electricity from coal or natural gas fired power plants, or heat our homes with oil, we release carbon that has been stored in the earth for millennia. In the combustion process, the carbon combines with oxygen to form carbon dioxide (CO2), a greenhouse gas. For hundreds of thousands of years, the CO2 concentration in the atmosphere never rose much above 280 parts per million. Since the industrial revolution, though, atmospheric concentrations of carbon dioxide have increased by 30 percent.
Over the same period, atmospheric methane has risen by 145 percent, mostly from agricultural activities like growing rice and raising cattle. Methane is a potent greenhouse gas - twenty times as efficient at trapping heat as CO2. But CO2 remains stable in the atmosphere far longer (100 years) than methane and so has a longer-term impact on the climate.
As the concentration of these gases grows, more heat is trapped in the earth's atmosphere and less radiates back into space. This increase in trapped heat alters atmospheric processes and their interaction with the oceans and the land. And the climate - the product of that interaction - changes as well, causing altered weather patterns that bring unexpected rain or dry spells and sudden, severe storms.
| 4. IS GLOBAL WARMING UNDERWAY? | TOP |
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Evidence over the past decade suggests that warming is already underway; surface temperatures have warmed 0.9oF over the past century, and the warming has intensified in the past two decades. In the Northern Hemisphere, eight of the hottest years ever recorded occurred in the past decade. The three hottest ever were 1998, 2001, and 1995. Because of this, spring arrives two weeks earlier in the Northern Hemisphere today than 20 years ago.
There has been an increase in the overall area of the world experiencing moisture extremes, from 1900-1995 (flooding or drought). This is qualitatively consistent with changes expected from the observed global warming of 1 degree over the past century. By contrast, the world is predicted to warm by 2.5 to 10.4 degrees this century.
| 5. HOW DO WE KNOW THAT WE ARE CAUSING GLOBAL WARMING? | TOP |
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The answer to this question is primarily quoted from the text of a presentation summarizing the most recent progress in understanding the human role in global warming, by Robert T. Watson, Chair of the IPCC, from July 2001: http://www.ipcc.ch/press/COP6.5/COP-6-bis.htm . That internet address also includes several valuable plots.
Most of the observed warming of the last 50 years is attributable to human activities. Climate models are now advanced enough to accurately simulate the observed changes in annual mean global surface temperature accurately from decade to decade, over the past century. These models are advanced, taking into account the observed increases in the atmospheric concentrations of greenhouse gases, sulfate aerosols and the observed decrease in ozone in the lower stratosphere, in conjunction with changes in natural forcing (changes in volcanic activity and solar output).
Not only has the rise in average global temperatures exceeded what might occur simply by chance, but the pattern of change is consistent with the hypothesis of human-induced warming. Warming due to a buildup of greenhouse gases, for example, is predicted to cause sharper spikes in nighttime than in daytime temperatures. This pattern - which would not occur if warming were caused by increased solar energy - is, in fact, what scientists observe. Human-induced warming is also expected to cause an increase in extreme weather events - floods, droughts, heat waves - which have also increased dramatically in recent years.
| 6. HOW MUCH WARMER IS THE EARTH LIKELY TO BECOME? | TOP |
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The 1995 report from the IPCC projects that the earth's average surface temperature will increase between 2.5 and 10.4°F in the next 100 years. This is in addition to the increase of 0.5° to 1.1°F that has already occurred since 1860. Scientists predict that even if we stopped emitting heat-trapping gases now, the climate wouldn't stabilize for many decades because of the gases we've already sent into the atmosphere.
These figures, moreover, are planetary averages. Larger increases will occur in some regions, smaller increases in others. The US National Climate Assessment Program estimates that warming will be above average over the continental US (one model predicted a 10°F temperature rise by 2100).
| 7. IS THERE A SCIENTIFIC CONSENSUS ON GLOBAL WARMING? | TOP |
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The consensus has grown dramatically in recent years, to where there is little question among scientists that human activities are raising the temperature of the planet. In 1988 the United Nations Environment Program and the World Meteorological Organization set up the Intergovernmental Panel on Climate Change to examine the most current scientific information on global warming and climate change. The consensus statements of this panel, available in documents at http://www.ipcc.ch/press/speech.htm , make it clear that the scientific consensus is strong.
On June 6, 2001, an 11-member panel of the National Academy of Sciences (NAS) released "Climate Change Science: An Analysis of Some Key Questions," a report they prepared for President George W. Bush. This panel of top US scientists generally affirmed the conclusions of the IPCC. This report is interesting because it addresses several questions that were asked by policy-makers and skeptics of climate change, and is available at: http://www4.nationalacademies.org/onpi/webextra.nsf/web/climate
The few remaining dissenting voices, with very few exceptions, receive funding from the fossil fuel industry - coal and oil producers, automakers and utilities. For more information on this, see The Heat is On, by Ross Gelbspan.
| 8. WHERE CAN I LEARN MORE ABOUT THE SCIENCE OF GLOBAL WARMING? | TOP |
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More than 2,000 of the world's leading climate scientists, economists, and risk analysis experts from 80 countries contributed to the IPCC's most recent set of reports, collectively titled Climate Change 2001. The three reports are subtitled, Working Group I: The Scientific Basis; Working Group II: Impacts, Adaptation and Vulnerability; and Working Group III: Mitigation The IPCC Third Assessment Report. These reports are available online, in digital and print form, at: http://www.ipcc.ch/
A presentation summarizing the state of scientific understanding of global warming as of late 2000, by Robert T. Watson, Chair of the IPCC, from November 2000: http://www.ipcc.ch/press/sp-cop6.htm
A presentation summarizing the most recent progress in understanding the human role in global warming, by Robert T. Watson, Chair of the IPCC, from July 2001: http://www.ipcc.ch/press/COP6.5/COP-6-bis.htm
The Change in the Weather : People, Weather, and the Science of Climate, by William K. Stevens, 2001.
Is the Temperature Rising? The Uncertain Science of Global Warming, by S. George Philander, a renowned climate scientist at Princeton University - this is not a new book (1998), but serves as a great source of more detailed information for those interested in climate.
SCIENCE: TOUGH QUESTIONS, SIMPLE ANSWERS
| 9. IS ANTARCTICA MELTING? | TOP |
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Scientists look to the global mean temperature as their primary evidence for global warming. This is because climate varies naturally from one region to another, and the annual mean temperature can be warming drastically in one location, and cooling drastically in another.
Climate skeptics and environmentalists frequently refer to the northern and southern polar regions when trying to disprove or demonstrate global warming. In Alaska and Siberia, scientists have documented an alarming warming trend over the past several decades. At the same time, some climate skeptics and scientists point to cooling in some other northern regions. On Antarctica, in the Southern Hemisphere, ice sheets have been collapsing due to warming temperatures in some regions, while other regions have actually had growing ice sheets due to cooling.
The reason for these conflicting trends is that natural climate variability is generally very high at the poles. Also, because of their extreme cold climates, these are the regions where the least historical temperature data is available. As a result, our knowledge of polar climates is limited. Recent research suggests that climate in these regions naturally varies by a large amount over periods of several decades. Furthermore, climate varies spatially much more than in temperate regions. As a result, the poles are generally the last place that scientists look for unquestionable evidence of global warming.
| 10. IF THE PLANET IS WARMING, WHY WAS IT SO COLD THIS SUMMER? | TOP |
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Even as the planet's overall climate changes, weather - the state of the atmosphere at a given time and place - will continue to vary from day to day, season to season and from region to region. While the intensity of climate change varies from place to place, and year to year, there is no question that Earth's mean temperature is rising. The past decade appears likely to have been the warmest of the millennium (1000 years various proxy data sources), and included 8 of the 10 warmest years in the instrumental record (120 years).
| 11. WHAT DIFFERENCE WILL A 2.5-10.4F DEGREE CHANGE MAKE? | TOP |
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The most confusing thing about global warming is that every day, temperatures at a given location often fluctuate by a great deal more then 10F. Seasonally, temperatures can vary even more widely. So, why would an increase of several degrees make any difference?
A modest rise in the earth's average temperature could have dramatic effects. Over the past 10,000 years, the earth's average temperature hasn't varied by more than 1.8°F. During the last Ice Age, in which much of the North American continent was covered by a kilometer of ice, average temperatures were only 5° to 9°F cooler than those today.
Nor will an increase of a few degrees make for pleasantly warmer temperatures around the globe. Some regions may be affected more profoundly than others. According to the most recent IPCC report, climate change will lead to "decreased water availability for populations in many water scarce regions". Others may lose coastal wetlands through rises in sea level. Agriculture in low-lying areas, such as along the Mississippi River, could be severely affected by floods. Scientists predict that continued global warming is likely to result in:
- Sea level is projected to increase 8-88cm between 1990 and 2100
- The frequency of extreme weather events will increase, e.g., heatwaves, floods, droughts, fires, and increased tropical cyclone peak wind and precipitation intensities.
- Severe stress on forests, wetlands, and other ecosystems
- Damage to human health as mosquitoes and other insects spread diseases over larger geographical regions (think West Nile virus!)
- Disruption of agriculture and water availability due to changes in temperature and rainfall patterns
| 12. ARE THERE ANY BENEFITS TO GLOBAL WARMING? | TOP |
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Spokespeople for the fossil-fuel industry like to point out that carbon dioxide, far from being a pollutant, is "plant food." Some argue that increased carbon concentrations and warmer temperatures will enhance plant and tree growth, lengthen growing seasons and generally lead to more comfortable weather in temperate zones. But any beneficial impacts could easily be overwhelmed by such negative consequences as drought and insect infestation. It is, in fact, impossible to predict the myriad ways climate change will impact the planet and neither climate scientists nor coal industry spokesmen know what the net effect on human life will be. Ecologist Herman Daly has proposed that environmental policy be guided by the rule that we do not destroy what we cannot now replace. Most would agree that the planet's climate is irreplaceable.
| 13. IS THE OZONE HOLE RELATED TO GLOBAL WARMING? | TOP |
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Global warming and ozone depletion are two separate threats, although some gases contribute to both. Chlorofluorocarbons (CFCs), for example, are the principal cause of ozone depletion, and they are also potent heat-trapping gases. In fact, the chemicals used to replace CFCs, such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs, now widely used in automobile and domestic air conditioning systems), may be an added source of global warming, since they are potent heat-trapping gases and their concentrations in the atmosphere are rising quickly.
But these gases are responsible for less than 10 percent of total atmospheric warming. Carbon dioxide, on the other hand, accounts for two-thirds of excess greenhouse gases. While reducing atmospheric concentrations of CFCs is crucial to preventing continued destruction of the ozone layer, it won't in itself solve the problem of global warming.
ECONOMICS, POLITICS
| 14. WHAT CAN WE ALL DO ABOUT GLOBAL WARMING? | TOP |
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The most important action we can take is to reduce emissions of heat-trapping gases. Governments, businesses, and individuals can all help. Governments can adopt a range of options for reducing fossil fuel burning, including implementing energy-efficiency measures, instituting policies that encourage the use of renewable energy sources (such as wind and solar power), and eliminating subsidies that encourage the use of coal and oil by making them artificially cheap. Governments must also do more to preserve old forests, which remove carbon dioxide from the atmosphere through photosynthesis.
| 15. BUT WON'T CUTTING EMISSIONS DESTROY THE US ECONOMY? | TOP |
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Credible economic studies of climate stabilization measures find a range of possible outcomes: from modest overall benefits, to modest costs. How would the economy benefit? As electric utilities develop renewables, as businesses retrofit factories to operate more efficiently, as consumers replace appliances, as firms insulate and upgrade buildings - all of these will generate new jobs and incomes in a wide variety of trades. Studies by both the Tellus Institute and the EPA estimate that CO2 reduction policies will result in a modest but significant increase in jobs over the next decade. Economist Janet Yellen, while Chair of Council of Economic Advisors testified to Congress that she does not "anticipate any significant aggregate employment effect" from reducing greenhouse gas emissions. Sharply reducing our use of oil and coal will certainly harm the oil and coal industries and any plan to address global warming should include retraining and assistance for displaced workers in those industries. But no credible models find costs large enough to seriously harm the US economy. And almost economists who study climate change believe that, on a benefit-cost basis, action should be taken now to begin curbing emissions. In a recent Science article, Professor William Nordhaus, a prominent economic analyst of global warming from Yale University, concluded that the US should re-engage with the rest of the world and create a framework for cutting emissions.
| 16. BUT WON'T EMISSIONS REDUCTIONS LOWER OUR STANDARD OF LIVING? | TOP |
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Americans today use two times as much energy per capita as do residents of Japan and Europe, whose living standards are quite similar. Simply by applying known efficiencies already in use elsewhere, we could cut our fossil fuel consumption by 20% or more. Further reductions can be made by shifting from fossil fuels to renewable energy-- like solar, wind and biomass, without cutting back on overall energy use. Switching to renewables will also reduce other sorts of pollution caused by fossil fuels - like smog, acid rain, strip mining for coal, oil drilling in sensitive habitat, and oil spills.
| 17. THIS IS OVERWHELMING! CAN WE REALLY SOLVE THIS PROBLEM? | TOP |
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We don't have much choice if our children and grandchildren are to inherit a stable planet. Humans have confronted other momentous problems - from the spread of Nazism in Europe to the hole in the ozone layer. We have also devised new technologies - electricity, antibiotics, computers - and seen them transform lifestyles in the course of a generation. Many of the technologies needed to stabilize the climate exist already and international discussions to reduce greenhouse gas emissions are underway.
| 18. WHAT CAN I PERSONALLY DO ABOUT GLOBAL WARMING? | TOP |
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Each of us can do simple things like turning off lights and appliances, driving less, using heat, hot water and air-conditioning more conservatively. Some states' utility companies offer a renewable electricity option, where one can elect to have a percentage of electricity come from wind or solar power. We can push our state and local government to cut their own emissions and press our national representatives to negotiate and ratify international agreements like the Kyoto protocol. Educate your neighbors and friends. Join a local environmental organization. Ask your representative what s/he is doing to address global warming. Small efforts, multiplied by hundreds of thousands of concerned citizens, can add up to massive social change.
Businesses, too can help, by increasing efficiency. At the same time, they will save substantial sums of money by reducing their energy expenses. Utilities can avoid building expensive new power plants by encouraging and helping customers to adopt efficiency measures.