Human actions are responsible for warming the Earth, reconfirms the landmark Intergovernmental Panel on Climate
Change (IPCC) report released today, the first mammoth report on the physical science of climate change issued in seven years. Scientists now say they are 95-100 percent certain that human actions—such as burning fossil fuels and cutting down forests—are behind the observed rise in global temperatures since at least 1950. Average temperatures have risen 0.85 degrees Celsius since 1880, but the new report warns that depending on how much more fossil fuels are burnt, temperature rises could exceed 4 degrees Celsius (9 degrees Fahrenheit) with untold consequences for global society.
“Boil down the IPCC report and here’s what you find: climate change is real, it’s happening now, human beings are the cause of this transformation, and only action by human beings can save the world from its worst impacts,” U.S. Secretary of State, John Kerry, said in a statement. “This isn’t a run of the mill report to be dumped in a filing cabinet. This isn’t a political document produced by politicians. It’s science.”
Indeed for those following climate science over the decade, none of this is particularly surprising: scientists have become increasingly confident that not only has the Earth warmed significantly in the last hundred years, but that radiative forcing due to greenhouse gas emissions is the main culprit. Other theories, one by one, have been largely disproved. Moreover, scientists have become increasingly assured that climate change will not only raise sea levels and melt glaciers, but also make extreme weather events more common and more intense, upend regional weather patterns, and force countless species to migrate or go extinct. In the end, scientists say the world will not only become warmer, but increasingly unstable and treacherous.
Wildfire in California. Increased drought and shifting rains due to climate change are expected to cause more severe wildfires in some regions. Photo by: Bureau of Land Management.
“Global surface temperature change for the end of the 21st century is projected to be likely to exceed 1.5 degrees Celsius relative to 1850 to 1900 in all but the lowest scenario considered, and likely to exceed 2 degrees Celsius for the two high scenarios,” said IPCC co-Chair with Working Group I, Thomas Stocker. “Heat waves are very likely to occur more frequently and last longer. As the Earth warms, we expect to see currently wet regions receiving more rainfall, and dry regions receiving less, although there will be exceptions.”
Governments worldwide have already committed to preventing the world’s temperature from going above 2 degrees Celsius over the Twentieth Century average, a threshold that if passed could lead to catastrophic climate change. However, while governments have made the commitment, few, if any, have sufficiently tackled the cause: greenhouse gas emissions from burning fossil fuels.
To this end, for the first time, the IPCC has endorsed a number of how much total carbon can be emitted into the atmosphere to stay below 2 degrees Celsius rise: 800-880 gigatonnes. But humanity has already spent over 60 percent of this (530 gigatons as of 2011), meaning that much of the world’s remaining fossil fuel deposits (including coal, gas, and oil) will have to remain in the ground—unburnt and unexploited—in order to avoid catastrophic consequences.
“This is yet another wakeup call: those who deny the science or choose excuses over action are playing with fire,” said Kerry. “Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or commonsense should be willing to even contemplate.”
The report did not shy away from recent findings that global warming has slowed over the last 15 or so years, at least beyond expectations. The IPCC acknowledges that warming has not occurred as fast as many models predicted, but noted that this is likely due to a number of factors. For one thing, comparing current temperatures to the extra hot year of 1998—which was drive by El Nino conditions—has made it appear that temperatures have stagnated, when in fact every decade over the last three decades has been warmer than the last. In addition, they view the slower rate of temperature rise as a short-term trend that is not expected to last, perhaps caused by recent volcanic eruptions, which have a cooling effect, or by extra heat being taken in by the deep oceans. According to the report, around 90 percent of the heat from greenhouse gas emissions ends up in the ocean.
The head of IPCC, Rajendra Pachauri, chair of the IPCC, told Reuters that scientists would need to see the current slower rate of warming last for three to four decades before they would consider it a new trend and adjust expectations accordingly.
Even as climate denialists have spent recent weeks attempting to dive bomb the IPCC report’s findings—which runs 2,500 pages, cites over 9,000 studies, and involves hundreds of scientists from around the worldwide—with a run-up of op-eds including pseudo-scientific claims and allegations, many climate scientists who actually work with the IPCC say the group’s work is, if anything, too cautious.
“The IPCC is far from alarmist—on the contrary, it is a highly conservative organization,” Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany told the New York Times. “That is not a problem as long as the users of the IPCC reports are well aware of this. The conservatism is built into its consensus structure, which tends to produce a lowest common denominator on which a large number of scientists can agree.”
U.S. carbon emissions are second only to those of China. Historically, the U.S. is the world’s largest carbon emitter. To date, the U.S. has no federal legislation to reduce its carbon emissions. Click image to enlarge.
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