The newest edition of the congressionally mandated climate assessment was released on Nov. 23. The report was written by more 300 scientists, with 13 federal agencies involved, and has already undergone rigorous peer review.
It’s an update for policymakers and the public on where we stand with climate change, where we’re most likely headed, and what might be done to mitigate the mean warming climate’s worst impacts. Technically, the release was made public by the White House, though most of its findings are starkly at odds with President Trump and his views on environmental deregulation.
For example, the report warns if significant steps are not taken to reduce our mean warming, the U.S. economy could shrink by as much as 10 percent by 2100. As I’ve noted in many past articles, the steps and impacts still have to be examined on a global basis, rather than just what the United States can do.
The United States has, after all, experienced some significant reductions in our greenhouse gas emissions due mainly to economic factors such as the lower cost of natural gas for electric utilities compared to coal. The reductions from utilities will slow in coming years because the switchover to natural gas is well advanced.
But this report, by its congressional mandate, has to focus on U.S. impacts and U.S. actions. As summarized in The New York Times and other sources, the 1,656-page report warns impacts in the United States will include more frequent and more devastating wildfires in California, more crop failures in parts of the plains and Midwest and a more rapidly crumbling infrastructure, particularly in the southern United States. With crop failures comes a likely disruption in the export and import chains for U.S. crops and foodstuffs and, by 2050, a reduction in crop yields to 1980s levels with a larger population. At about the same time, the 13-agency assessment reports wildfire seasons could be extending into parts of the southeast.
As Woods Hole Research Center president Philip Duffy told The New York Times, “There is a bizarre contrast between this report, which is being released by this administration, and this administration’s own policies.”
Scientists who worked on the report said they are unaware of administration efforts to alter or suppress the report’s content, though a few questioned the timing of its release on the afternoon after Thanksgiving, according to the Times.
This is the first U.S. Climate Assessment Report to put more precise numbers on the economic costs of projected climate impacts: $141 billion from heat-related deaths, $118 billion from sea level rise, and $32 billion from climate-related infrastructure damage.
Actual outcomes will depend on how quickly and effectively the U.S. and other nations act to reduce carbon dioxide and methane emissions, and how much is spent on impact mitigation efforts. An example of the latter could be floodgates to protect the New York harbor and the nation’s financial district from inevitably worse storm surges in future disastrous events like Sandy.
Since impacts are already well underway across the country in varying degrees, the report covers all regions of the United States for future impacts. They include predictions that saltwater will begin to contaminate drinking water in Puerto Rico and the Virgin Islands (other reports have included south Florida and the Gulf Coast), droughts reducing hydropower output in the west as well as reducing water supplies and the loss of sea ice leading to coastal flooding and the relocation coastal communities in Alaska.
In the Midwest and northeast, heavy precipitation flooding events are on the rise and will continue to increase. One example cited was the 2011 Missouri River flood, which inundated a nuclear power plant near Omaha, shutting it down for years. This regional increase in heavy precipitation impacts was well predicted by earlier climate models.
The recent UN Intergovernmental Panel on Climate Change report warned of dire impacts globally, but struck an almost idealistic note of optimism IF we and other industrialized nations moved very quickly (and very expensively) to drastically slash fossil fuel related greenhouse emissions and began constructing protective infrastructure.
For me, the bullet points of this report are made all the more disturbing by the breadth of the academic disciplines involved among the 300+ authors. There is far more than climate science behind this massive work. There is social and behavioral science, engineering, hydrology, architecture, urban planning, political science, along with all the traditional related scientific disciplines involved in tracking climate change. In particular, I was struck by the significant projected negative effects on the nation's economy, including trade and agriculture. It is truly a multidisciplinary document.
In the meantime, here is where we stand on human-related greenhouse gas emissions, starting with the relationship between the increase in carbon dioxide and temperatures since 1880.
And finally, here is the NOAA derived climate-related Extreme Weather Index and where most of the excess heat is being stored, with eventual feedback mechanisms.