Global Warming & Climate Change
What does “global warming” mean?
Global warming means that the average temperature of the air near the earth’s surface has risen—by about 1.4º Fahrenheit during the 20th century—and seems likely to keep rising.
What is the mainstream scientific opinion about global warming?
Nearly all scientists agree that this warming trend exists. In a 2007 report, the Intergovernmental Panel on Climate Change (IPCC) stated that most of the temperature increase since the mid-20th century was “very likely” caused by human activities—especially the burning of fossil fuels, such as coal and gasoline, and the cutting of trees in tropical forests. The IPCC defines very likely as a 90% probability.
In 1997, more than 1,500 of the world’s leading scientists signed a petition that called global warming “one of the most serious threats to the planet and to future generations.” The petition urged governments to take action to reduce their emissions of gases believed to cause global warming.
The national academies of science of all major industrialized countries have endorsed the IPCC’s findings. Not every scientist agrees with the majority’s opinions, though.
What’s the disagreement about?
A minority of scientists question how much of global warming is due to human activity. Others disagree about how severe the effects of climate change will be, and about what we should do, if anything, to slow down global warming. Some say that adapting to the coming changes would be more efficient than trying to stop them. A very small number of scientists doubt that global warming is actually happening.
It’s important to note that, among climate scientists, there is widespread agreement that human activity has caused global warming—and that the trend can be reversed if we make a concerted effort. Media attention to the controversy, however, has left the public more skeptical than the scientists. In a 2009 poll, 84% of scientists agreed that human activity is contributing to global warming, while only 49% of the public agreed.
Oil companies such as ExxonMobil, whose business depends on our continued use of fossil fuels, have funded scientists who dispute the majority opinion and organizations that dismiss global warming as a myth.
Among American politicians, the disagreement has generally broken down along party lines, with many Republicans expressing skepticism about human activity contributing to global warming, and most Democrats accepting the majority scientific view.
Possible results of warming and climate change
The IPCC predicts that the temperature will rise another 2 – 11.5º Fahrenheit by the end of the 21st century. The change may sound minor, but it would mean a bigger and faster rise in temperature than any the Earth has seen in the last 10,000 years. Melting ice would likely cause sea levels to rise by as much as two feet by the end of this century. (The summer Arctic ice cap has already shrunk by more than 20% since 1979.) As a result, storms would become more severe, and frequent floods would hit coastal regions. Some areas would get more rainfall, others would experience drought and heat waves. Air quality in cities would get worse, because heat intensifies smog. Some species would become extinct as a result of changes in their habitat.
It’s important to understand that local storms, cold spells, and heat waves can’t be clearly attributed to global warming. Instead, scientists predict more extreme weather in general around the world.
The greenhouse effect
A natural phenomenon, the greenhouse effect helps regulate the temperature of the air. A layer of clouds and greenhouse gases traps the warming rays of the sun in the atmosphere near the Earth’s surface. Without this layer, the planet’s surface would be too cold for us to survive. Most scientists believe it’s very likely that burning fossil fuels adds enough CO2 to the atmosphere to trap more heat and raise average temperatures around the world.
How does burning fuel cause global warming?
Coal and gasoline have their origins in organic matter: plants and animals that died in prehistoric times, decomposed, and were transformed over millions of years. When these fuels are burned, the carbon in them escapes into the air as carbon dioxide, or CO2. Carbon dioxide is one of a few greenhouse gases that contribute to the greenhouse effect. According to the mainstream view, the more carbon dioxide we release into the atmosphere, the thicker the blanket gets, and the warmer the earth becomes.
Cutting down large numbers of trees also has an impact on the amount of CO2 in the atmosphere. Plants take in carbon dioxide and release oxygen; when forests are cleared (for timber, farmland, or development), that removes an effective tool for keeping CO2 levels down.
But it’s been so cold this spring…
If it’s unusually cold in certain parts of the country, does that mean global warming is a myth? Many people wonder. Here’s what climate scientists say:
Global warming is a trend over the planet as a whole. On average, the 2000s were warmer than any previous decade since records have been kept, but some areas experienced cooler temperatures than normal. We’re seeing more record-breaking hot days, and fewer record-breaking cold days, and that trend seems likely to escalate.
3/31/11: Richard Muller, a respected physics professor at the University of California, Berkeley, has been prominent among those who argue against anthropogenic (human-caused) climate change, because he expressed doubts about the data on which the theory is based. Testifying before a congressional committee on his own research, however, Muller said, “We see a global warming trend that is very similar to that previously reported by the other groups.” For more, see Science magazine.
4/19/11: The Supreme Court heard arguments in American Electric Power Co., Inc. v. Connecticut, a landmark case in which eight states argued that they had the right to sue four power companies (responsible for 25% of the U.S. electric power industry’s CO2 emissions) for contributing to global warming and thus creating a public nuisance. The states are seeking to force the utility companies to reduce their emissions.(For more on the case, see SCOTUSblog, which covers the Supreme Court, and this New York Times editorial.)
6/20/11: The Supreme Court unanimously rejected the lawsuit (American Electric Power v. Connecticut) aimed at forcing major electric utilities to reduce their greenhouse gas emissions before federal regulators took action. For details, see the New York Times.
5/9/13: The concentration of carbon dioxide in the earth’s atmosphere has exceeded 400 parts per million — probably for the first time in 3 million years. The last time it was at that level, the planet was about 5°F warmer and sea level was at least 30 feet higher. For more, see National Geographic.
Terms to know
Fossil fuels: substances containing carbon, that can be used as fuel. Fossil fuels were formed by geological processes acting on decayed plants and animals that lived hundreds of millions of years ago. Petroleum, coal, and natural gas are all fossil fuels.
Greenhouse gases: gases that contribute to the greenhouse effect. They include water vapor, carbon dioxide, methane, and ozone, among others.
IPCC (Intergovernmental Panel on Climate Change): a group of the world’s leading climate scientists and other experts. Created by the U.N. in 1988, the IPCC shared the 2007 Nobel Peace Prize with Al Gore for alerting the world to global warming.
The Kyoto Protocol: the main international agreement to reduce greenhouse gas emissions. Adopted in 1997, the Protocol requires 37 industrialized countries to reduce their emissions of four greenhouse gases. So far, 187 nations have signed and ratified the agreement. As of 2010, the U.S. is the only major industrialized nation that has refused to ratify it. The reason: under the Protocol, China and India (with their rapidly expanding economies, and growing emissions) are not required to reduce or limit their emissions. American officials fear that we will put ourselves at a competitive disadvantage if we cut our emissions and our rivals don’t. (For more on the Kyoto Protocol, see Wikipedia.)
The Copenhagen Accord: a document that delegates to the 2009 U.N. Climate Change Conference agreed to “take note of.” The Accord acknowledged the need to keep temperature increases to no more than 2ºC, but included no commitments to decrease emissions: therefore, many climate change activists consider it a failure. Under the Copenhagen Accord, the nations of the world also agreed to a goal of raising $100 billion per year by 2020 to help developing nations cut their carbon emissions; but this is only a goal, and is not legally binding. For more on the Accord, see Wikipedia and this article.
Cap and trade: a system in which emissions limits are set, and companies and organizations that don’t emit their allotted amount can sell credits to those that have exceeded their limits. In order to reduce emissions, the overall limits would be lowered over time.
An issue of justice
The people likely to suffer most from climate change are those who live in the poorest countries in the world. Ironically, these are the countries that contribute least to the emissions that cause global warming, and their citizens have not enjoyed the comforts (such as abundant electricity and car ownership) that result in greenhouse gas emissions. Under the Kyoto Protocol, these developing countries are not required to reduce or limit their emissions.
China and India: a developing problem
China and India account for about a third of the world’s population. Both countries have long been poor, but their economies are growing quickly. That means more cars, more electricity—and more greenhouse gases. The U.S. insists that China, which now emits more CO2 than the U.S., must do its share to reduce emissions. China responds that its emissions per person are still far lower than in the U.S., and that its citizens have the right to a higher standard of living.
Which term is preferable, global warming or climate change?
Global warming refers only to rising temperatures. Climate change also includes other changes that may result from higher temperatures. There’s another difference, too: global warming is a concept that skeptics have attacked, resulting in public uncertainty about whether it’s real or an exaggerated threat, while the phrase climate change is still relatively free of negative associations.
How should we respond to climate change?
Activists and observers have pointed out that, even if scientists don’t agree on every aspect of climate change, the risk of catastrophe calls for a strong response. They argue that, if we don’t act now, the results will be much more expensive (or impossible) to reverse later; that developing alternative energy will create business opportunities; and that other countries are already moving ahead with new energy technology, leaving us to catch up.
More conservative commentators say the cost of reducing emissions will outweigh the benefit, because even huge investments may produce only small results.
Responses to climate change fall into three general categories: reducing future greenhouse gas emissions, adapting to change, and engineering to reverse global warming.
• Reducing emissions: We burn fossil fuels to generate electricity, to power cars, trucks, trains, and aircraft, and to heat our homes and workplaces. Each year in the U.S., coal-burning power plants emit 2.5 billion tons of CO2, and cars emit 1.5 billion tons. The majority of scientists agree that we need to change the way we generate power, build more efficient cars, and cut our electricity use through improved energy efficiency.
• Adaptation: Whether or not emissions are reduced, we will need to adapt to climate change. Possible adaptations include: abandoning areas threatened by rising sea levels; building flood defenses; and even installing more air-conditioning (which, however, would make the problem worse, because powering the air-conditioners would put more CO2 in the air).
• Geoengineering: Some scientists think it may be possible to engineer solutions, by reducing either the amount of solar radiation that reaches the earth, or the amount of CO2 in the atmosphere. For more on geoengineering to combat global warming, go here.
• In addition, protecting forests and planting more trees would help reduce the amount of carbon dioxide in the atmosphere, since plants absorb CO2 and release oxygen.
What can individuals do to help?
• Choose the car that gets the most miles per gallon. If you have more than one car, use the most fuel-efficient one more than the others.
• Change your incandescent light bulbs to compact fluorescents. Each compact fluorescent bulb uses so much less electricity than an incandescent that it results in almost 700 pounds less CO2 released into the air over its lifetime.
• When buying new refrigerators, air-conditioners, and other appliances choose the most energy-efficient ones you can find. Look for the Energy Star label, which means that the appliance uses at least 15% less energy than the legal requirement.
Richard Muller, “The Conversion of a Climate-Change Skeptic,” New York Times, 7/28/12: “Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause… [Next] comes the difficult part: agreeing across the political and diplomatic spectrum about what can and should be done.”
James Hansen, “Game Over for the Climate,” New York Times, 5/10/12: “If we were to fully exploit [Canada’s tar sands], and continue to burn our conventional oil, gas and coal supplies… [the] level of heat-trapping gases would assure that the disintegration of the ice sheets would accelerate out of control. Sea levels would rise and destroy coastal cities. Global temperatures would become intolerable. Twenty to 50 percent of the planet’s species would be driven to extinction. Civilization would be at risk… This is why we need to reduce emissions dramatically.”
“Surveyed scientists agree global warming is real,” CNN.com, 1/20/09: “The strongest consensus on the causes of global warming came from climatologists who are active in climate research, with 97 percent agreeing humans play a role.”
A roundup of media coverage on whether or not the tornadoes of spring 2011 are a side-effect of global warming.
“We’re treating our atmosphere like we once did our rivers. We used to dump waste thoughtlessly into our waterways, believing that they were infinite in their capacity to hold rubbish… Our atmosphere has limits too.” —Union of Concerned Scientists
“The impact of Kyoto-like proposals will be too small for we scientists to measure due to the natural variations of climate… Additionally, the climate system is immensely complicated and really cannot be tweaked for a predictable outcome.” — John Christy, climate scientist
Ready to learn more? Start with these links:
Is climate change responsible for storms like Sandy? Yes and no: see this Washington Post article for an explanation.
To calculate your household’s greenhouse gas emissions: the E.P.A.’s Individual Emissions page
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Last updated 5/13/13
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