Michael Oppenheimer on the IPCC’s Fifth Assessment Report: When Will Global Warming Become Dangerous?

Pace Law School had the privilege of hosting Dr. Michael Oppenheimer for an hour-long lecture on the Intergovernmental Panel on Climate Change’s Fifth Assessment Report. Dr. Oppenheimer was the lead author of the Fourth Assessment Report, and is a coordinating lead author of SREX (a special IPCC report on managing the risks of extreme climate events). Dr. Oppenheimer is currently the Albert G. Milbank Professor of Geosciences and International Affairs in Princeton University’s Woodrow Wilson School and Department of Geosciences. Before Princeton, Dr. Oppenheimer spent more than 20 years at the Environmental Defense Fund.


Dr. Oppenheimer began his lecture, as the Firth Assessment Report begins, with a description of the planet’s greenhouse effect and distinguishing the greenhouse gas problem caused by humans. Dr. Oppenheimer pointed to two now well-known lines of proof for global warming: (1) temperature measures by continent are all rising, and the climate models are reproducing the same increase (this gives them credibility); and (2) greenhouse gas levels and temperature changes track together historically. Dr. Oppenheimer likened the greenhouse gas problem to a bathtub, saying that human-made carbon dioxide and other greenhouse gases emitted into the atmosphere behave like water in a bathtub with a blocked drain: we just keep pumping them into the atmosphere and eventually their concentration will “overflow.” We are already seeing a lot of consequences of increased greenhouse gas concentrations—for example, the Arctic ice is very cracked and fragmented, when it used to be a solid sheet of ice. This is the biggest problem of the 21st century.


A fundamental component to the problem is how government handles risk—frequently, it is a step too late. Risk also includes the human side (how smart are we? How will we adjust?), not just the threat to the environment. Through the IPCC, national governments have claimed the climatic danger zone is an increase in global temperature of more than 2o Celsius, which corresponds to 400-450 parts per million of carbon dioxide in the atmosphere. We have already reached 400 parts per million; maintaining business as usual has the planet seeing a rise of 3-6o C.


Dr. Oppenheimer highlighted three particular risks from the Fifth Assessment Report that the planet faces as the climate changes, and which will be particularly aggravated if greenhouse gas emissions are not aggressively curbed: the heat index, crop yield, and coastal flooding. Dr. Oppenheimer discussed the heat index by using the concept of a wet bulb temperature, which takes into account the humidity as well as heat. A wet bulb temperature of 92o Fahrenheit is when normal human activity outside is potentially deadly. Under business as usual, this heat index risk will become a huge threat beyond the year 2100, when a significant portion of the summer is projected to see wet bulb temperatures in the deadly zone. Dr. Oppenheimer stated that crop yield declines are outpacing crop yield increases. This is because the benefits of the green revolution are running dry and because of the effect of a changing climate. Crop yields and food supplies will become a serious threat if the planet warms 3-4o C. Coastal flooding is a big risk because of the combination of stronger storms and higher sea levels; we will be seeing water where it hasn’t been before. This combination also has a multiplier effect: the hundred-year storm and flooding levels will happen every 1-10 years instead.


Dr. Oppenheimer then discussed the need to reduce greenhouse gas emissions on a global level; adaptation, while critical, is not enough on its own. Dr. Oppenheimer highlighted the recent agreement between the United States and China to each reduce their greenhouse gas emissions by three percent every year. While certainly a tall order, it is within the realm of doable. Any greater annual emissions reductions, Dr. Oppenheimer stated, is virtually impossible. Dr. Oppenheimer illustrated the importance of reducing greenhouse gas emissions by noting that we have already used about 65 percent of the planet’s total carbon budget (and the US has consumed the majority of that used portion). With China, India, Brazil, and other countries rapidly developing, we risk using up the remainder of the total carbon budget at a much faster pace, therefore realizing catastrophic climate change more quickly. The need to significantly reduce greenhouse gas emissions is quite acute.


Dr. Oppenheimer ended with a poignant point: in spite of the notable risks and danger, we forget. Always. And much too quickly. Dr. Oppenheimer used flooding in the Hoboken subway station as a local example. In 1992, the station flooded as a result of a powerful storm. Immediately after, there were discussions and plans to storm-harden the station; ultimately, nothing of substance wound up happening because time went on and the memory of danger faded. Ten years later, Superstorm Sandy hit, and the Hoboken station saw the same flooding. We forget, perhaps because we inherently do not want to focus on threats and dangers for so long, for the amount of time necessary to see an actual solution to bulk up our resiliency and lower future risks. However, as Dr. Oppenheimer’s lecture very clearly illustrated, the changing climate is a threat we should try our hardest to not forget.



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