Global Warming FAQ
Sherwood Research Group - Yale University
Is "global warming" really happening? No question. Every global indicator shows warming: retreating sea ice, melting glaciers, pole-ward species migrations, upward tree-ring-derived temperatures, and earlier spring thaws (). The global average temperature now is about 1.2 F warmer than 100 years ago and probably the warmest in at least a millennium. Is recent, weird weather due to climate change? Weird weather has always, and will always happen. The media love to dwell on it, making it seem worse than it is. No one event can be blamed on any particular culprit. But some aspects of the weather (see below) are getting a boost from climate change. What about the ozone hole? Is that causing climate change? No, that's a separate problem. It was successfully addressed through an international agreement to phase out freon-type gases in refrigerators, air conditioners and spray cans. Don't temperatures swing naturally? Yes, but as far as we can tell this can't explain recent changes. Yes: 55 million years ago the north pole was as warm as Florida today; 20 thousand years ago, much of North America was under miles of ice. However, many scientists have tested the hypothesis that the recent warming is also a natural shift. Every analysis has yielded the same answer— "no"—the warming since 1970 has been too widespread and too rapid. So what's causing global warming? Fossil fuel burning is the biggest contributor. Scientists have predicted that this would warm the planet by adding to the atmosphere carbon dioxide, a so-called "greenhouse gas" that absorbs infrared radiation, inhibiting planetary cooling. Greenhouse gases are naturally present, and without them we'd all freeze, but we've added a lot more. Every calculation has predicted a substantial warming--between 3 and 8 F--if atmospheric carbon dioxide is doubled from 0.028% to 0.056% of the atmosphere. It's currently 0.038% and climbing fast. Are we sure carbon dioxide is actually rising, and that burning fossil fuels is the cause? Absolutely. We now have very accurate histories showing little change for millennia, then a meteoric rise after coal came into wide use in the early 1800's. Carbon-14 measurements also confirm that the added gas comes from ancient fossil fuels. Other greenhouse gases like methane followed a similar trajectory, though their sources are more complicated. Could plants absorb the extra carbon dioxide? They are absorbing some—otherwise atmospheric amounts would be rising even faster. Widespread forest planting would help, but only enough to delay warming by maybe a decade or so, and only if the land remains unneeded for other uses. Unfortunately, future warming will probably work against us by causing soils to start releasing stored CO2.
How will a warming climate affect us? This is a matter of considerable uncertainty and debate, but large climate changes will surely be disruptive. Obviously we'll have milder winters and hotter summers. In addition: Longer growing seasons (good for farming) Less snow and more rain (very bad for summertime water supplies in much of the world including the Western US) Less reliable, but heavier rains (bad for farming and flood control) Shifting storm tracks (bad for southern Australia, New Zealand, Chile, Argentina, and probably sub-Saharan Africa) Failing health of old-growth forests and other ecosystems Rising sea levels and displaced coastal populations The Unexpected Isn't there scientific disagreement about global warming? The legitimate disagreements are over details. All reputable scientists, even outspoken "skeptics" acknowledge that we have caused greenhouse warming and it will continue. Uncertainty or disputes are limited to the severity of future changes, and the extent to which certain recent trends (like the loss of the snows of Kilimanjaro) are attributable to greenhouse gases. There are a few quacks who will dispute even the basic points, in public or before Congress, but usually not among scientists because of the ridicule that would follow. Unfortunately some groups invested in the status quo are running disinformation campaigns to confuse the public.
Should we act now, do we have time to "wait and see", or is it already too late? It is too late to prevent some more climate change in the next few decades, but not too late to forestall severe consequences for our grandchildren and generations after them. The goal is to keep warming to less than about 3-4F in order to prevent the eventual melting of Greenland. The US, China and India are gearing up to rapidly expand their electricity generation and refining capacity, and they are currently planning to stick with old, polluting 20th-century technology even though others are available. This would be a disaster, an additional belch of greenhouse gases over the next few decades that would more than double our previous emissions and guarantee more serious impacts down the road. Now is a pivotal time in world history.
What you and I can do:
Talk about this problem with friends. Confront your elected representatives. Purchase everything with energy efficiency the key criterion. This includes cars, appliances, and investments—everything! Actively pursue the use of green technologies in cars, homes and elsewhere. Turn down the A/C. If we shop or work in over-cooled places, let's complain Support science education and media coverage. Scientific ignorance is an important part of this problem. Campaign and vote for candidates who promote policies to address global warming.