Copenhagen and the Diversion of Hacked Emails
The leaders of nearly two hundred countries have departed Copenhagen, and the results from the Fifteenth Meeting of the Conference of Parties are mixed. One thinks of the opening of Charles Dickens’s A Tale of Two Cities:
“It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to heaven, we were all going direct the other way - …”
Would more have been accomplished, if a series of private emails between climate researchers had not been hacked and released? It certainly was not a pretty picture, and it also was a confused picture with some critics claiming that the hacked emails revealed that the very foundations of climate science are suspect—maybe even fraudulent.
It’s hard to ignore the timing of the release of the hacked emails, which apparently was intended to have an impact on the proceedings at Copenhagen. And they did appear, at least in the United States, to have been a serious distraction. So on behalf of scientists from around the globe who have devoted years of study to understanding climate change, and for the sake of anyone just confused by this email controversy or climate change generally, I feel compelled to explain why the great majority of knowledgeable scientists are convinced that climate change poses a serious threat to us.
Here is what we know absolutely for certain: Carbon dioxide is a heat-trapping greenhouse gas. The amount of carbon dioxide in the atmosphere has increased by almost 40% since 1750, after being relatively constant for more than 5000 years. And the increase is due primarily to the burning of fossil fuels. On this, there is no scientific debate.
Back in the 1980s, though, there was little hard evidence about the expected consequence: that the increase in carbon dioxide and other greenhouse gases was leading to a warmer Earth. The changes in temperature were still too small to be seen clearly against the natural variations in temperature that take place from year to year and decade to decade—and indeed, the theory said any changes should be hard to detect at that point. Many scientists argued that global warming might not happen at all, for various reasons. These researchers were in the minority, but their ideas were plausible and had to be considered.
Since then, however, a great many independent lines of evidence have emerged that overwhelmingly indicate we live in a warming world. In the most recent assessment of the peer-reviewed scientific literature, the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report of 2007 found, among many other things, that:
Eleven of the twelve years between 1995 and 2006 ranked amongst the 12 warmest years since 1850 (we’ve since learned that the year 2009 is likely to rank in the top 10 warmest years and the decade of the 2000s was the warmest decade since record began in 1850), sea level is increasing, glaciers around the world are generally retreating, the Arctic is warming almost twice as fast as the global average, and Arctic sea ice is declining rapidly. In the biological world, plants are blooming and birds migrating earlier in the spring, growing seasons are getting longer, and plants and animals are moving toward the poles and to higher elevations.
Based on these observations and many, many others, the IPCC concluded that warming of the climate system is “unequivocal,” and that most of the observed warming since the mid-20th century is “very likely” due to the human-caused increase in greenhouse gases. In other words, the IPCC gave less than a 10% chance that the warming is entirely natural. An assessment today would almost certainly reduce those odds even further due to new evidence and recent research.
The way the IPCC is organized and operates insures that these statements represent the best available science. Each Assessment Report -- there have been four so far, with a fifth now in progress -- draws on many thousands of peer-reviewed papers on climate change, encompassing tens of thousands of datasets. Many hundreds of scientists then synthesize the findings into a report that even-handedly summarizes the collective knowledge the papers represent.
The peer-review process is not infallible. But in the end, the preponderance of evidence, filtered through peer review, is what moves us forward. It is the peer-review process that gave us the structure of DNA, the understanding that smoking causes lung cancer, the research that led to computers and Mars landers, and the science that explains earthquakes, black holes and hurricanes.
Peer-reviewed science is now clearly telling us that climate change is happening and that this change is primarily the result of human-caused increases in greenhouse gases. Arguments over particular lines of evidence are a crucial part of the ongoing process of understanding the subject; however, arguments over whether the planet is warming, most likely from human influence, ignore mountains of evidence.