The Weight of the Evidence: How We Know the Planet is Warming

This guest post is an excerpt from Cooler Smarter: Practical Steps for Low-Carbon Living, written by the Union of Concerned Scientists and published by Island Press. Find out more at

Standing at the Crossroads

The evidence that global warming is underway is not just persuasive, it’s overwhelming—the scientific equivalent of a slam dunk. Anyone who says otherwise is full of, well, hot air. The more we learn, the more we recognize that humanity really does stand at a crossroads today. Our failure to address this problem will imperil us all. The evidence is accumulating from diverse disciplines and from research teams in every corner of the globe. It is worth noting that the great majority of the scientists conducting this research do so out of passion for their subject matter, not as part of any political policy debate. Most of them would love nothing more than to find evidence that global warming is abating. But as we have seen, that is emphatically not the case.

That’s why it is so important—not just to our environment but also to our democracy—for each of us to learn as much as we can about the facts of global warming. The widespread lack of public understanding causes problems in several ways. First, it creates a gap between the nation’s citizens and the experts who study the problem on their behalf. Some climate scientists are so immersed in their specialized research they may forget that the public is not as conversant as they are with “carbon sinks” and “radiative forcings.” They don’t realize that most of us have never had a strong grasp of the basics.

But there is a more insidious problem, too: the lack of public understanding allows some powerful interests to milk the confusion so they can keep profiting from business as usual. This is not some wild conspiracy theory; it’s documented fact. A report published by the Union of Concerned Scientists in 2007, for instance, clearly demonstrates how ExxonMobil has, for years, poured millions of dollars into purposefully manufacturing uncertainty on climate change by underwriting the work of discredited spokespersons whose work couldn’t pass muster in legitimate, peer-reviewed scientific journals. Drawing on techniques perfected by the tobacco industry in the 1960s, ExxonMobil has worked behind the scenes to create or fund organizations with legitimate-sounding names— like the Committee for a Constructive Tomorrow or the Center for Science and Public Policy—specifically to publicize discredited views that are not supported by the science and to make their handpicked faux experts available to the media.

Of course, ExxonMobil is not the only player to employ this cynical tactic. But unfortunately for all of us, the disinformation has been remarkably effective in encouraging many people to believe there is some controversy or doubt among scientists about global warming when, in fact, there has been an overwhelming consensus for many years that the burning of fossil fuels by humans is driving disruptive climate change.

Thankfully, there’s an easy way to thwart overt disinformation. People who are informed about the facts won’t be misled by Exxon-style campaigns.

And as we put together the big picture from the disparate strands of evidence about global warming, it becomes increasingly clear that with carbon dioxide emissions on track to increase by some 43 percent above 2007 levels by the year 2035 (according to the U.S. Energy Information Administration), doing nothing is really not a viable option.

For one thing, evidence is mounting that global warming is leading to an increase in the incidence of extreme weather events. With rising temperatures, strong data already link global warming trends to an increase in the number and severity of heat waves. But the evidence also shows that the severity of intense precipitation events is increasing as well. This is because global warming is causing more evaporation of ocean water into the atmosphere as well as increasing the amount of water vapor the atmosphere can hold. High levels of water vapor in the atmosphere in turn create conditions more favorable to heavier precipitation in the form of intense rain and snowstorms. According to a recent assessment, for instance, between 1958 and 2007 the amount of rain or snow falling in the heaviest storms in the northeastern United States increased, on average, by 67 percent.

Similarly, while the data are still evolving on the link between global warming and hurricanes, the latest science suggests that hurricanes developing on the Atlantic Ocean are likely to diminish in total number but increase in intensity and drop more flood-producing rains inland, making it more likely for them to cause damage to populated regions.

There is no question that we will need to undergo a major transformation to contend with climate change. To be sure, there are many hopeful signs of this transformation. But given the number of powerful interests standing in the way, it is unlikely to happen quickly enough to avert the most devastating results of a warming planet unless there is pressure from the ground up on governments and corporations. They will need to step up and do more, but they are unlikely to do so until they see this groundswell. Making changes in your life to reduce your emissions sends an important signal to many others near and far. In other words, you have the power to make significant changes. And there’s no time to waste.

TreeHugger readers can get a copy of Cooler Smarter at a 30 percent discount. Simply head over to Island Press and use the coupon code 2Hug.

The Weight of the Evidence: How We Know the Planet is Warming
In this excerpt from the latest book by the Union of Concerned Scientists, the authors explain why we're standing at a climate crossroads&dmash;and how serious the next decision really is.

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