We all know the earth's climate is changing. The effects are inescapable no matter where we live. Here in New England, some changes are subtle (more humidity, consistently warmer nights), dramatic (more intense rainfall events), confusing (bigger snowfall events), and dangerous (more powerful hurricanes). The science tells us these are expected in a warming world, and indeed, we see them.
We also know that we are in the driver's seat for these changes. Our burning of oil, coal, and natural gas – fuels that have been extracted from fossil reserves buried in Earth's crust – is changing the composition of the atmosphere. Greenhouse gases constitute a tiny fraction of the atmosphere, but their ability to trap heat has made the difference between Earth being a frozen ice-ball of a planet and the relatively balmy one we inhabit. Greenhouse gases do this by preventing heat from escaping to space, just as a blanket tucked around a child at night keeps her warm. We are adding to this greenhouse gas blanket, and earth is warming up.
The most comprehensive accounting of the evidence can be found in the Intergovernmental Panel on Climate Change (IPCC) Assessments. The IPCC has begun to release the 5th Assessment Report and the latest installment has increased the certainty to 95 percent probability that humans are driving the observed and projected changes. The consensus of climate scientists from around the world is that the link between human actions and climate change is as strong as the link between smoking and cancer.
Still we hear in the media reports that global warming has stopped for the last 15 years; that increases in polar ice this year run contrary to the theory; and that an extreme cold snap puts a nail in its coffin.
