This month David W. Fahey of the US National Oceanic and Atmospheric Administration addressed the American Solar Energy Society Solar 2018 conference in Boulder, CO. He called attention to the highly authoritative new report, the fourth US National Climate Assessment . Volume 1 is out, Volume 2 will be published later this year.
Fahey explained that this assessment is mandated by Congress, and is a science report, not a policy document. It contains a summary of what we know about climate change (specifically in the US), with an emphasis on careful analysis of the evidence and unknowns.
This is similar in spirit and in results to the IPCC report except only by and about the US. Fahey was at pains to point out that the report was thoroughly reviewed (seven times!) and signed off by the US National Academy and by 13 departments and agencies.
He describes this as “us talking to us”.
The report itself is hundreds of pages long, the executive summary alone is 30 some pages. No, I have not had time to read it.
There is a two page “highlights” that I have read.
For anyone with even the least familiarity with climate science will not be surprised by the findings. The main report backs up these points with the best science available, as well as clear statements about just how good the science is.
The main points are extracted from the report:
This period is now the warmest in the history of modern civilization.
it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century.
Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor.
global average sea level has risen by about 7–8 inches since 1900, with almost half (about 3 inches) of that rise occurring since 1993
Global sea level rise has already affected the United States; the incidence of daily tidal flooding is accelerating in more than 25 Atlantic and Gulf Coast cities.
Global average sea levels are expected to continue to rise—by at least several inches in the next 15 years and by 1–4 feet by 2100. A rise of as much as 8 feet by 2100 cannot be ruled out.
Heavy rainfall is increasing in intensity and frequency across the United States and globally and is expected to continue to increase.
Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent.
over the next few decades (2021–2050), annual average temperatures are expected to rise by about 2.5°F for the United States, relative to the recent past (average from 1976–2005), under all plausible future climate scenarios.
The incidence of large forest fires in the western United States and Alaska has increased since the early 1980s and is projected to further increase
Annual trends toward earlier spring melt and reduced snowpack are already affecting water resources in the western United States
chronic, long-duration hydrological drought is increasingly possible before the end of this century.
The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally.
With significant reductions in emissions, the increase in annual average global temperature could be limited to 3.6°F (2°C) or less.
The global atmospheric carbon dioxide (CO2) concentration has now passed 400 parts per million (ppm), a level that last occurred about 3 million years ago, when both global average temperature and sea level were significantly higher than today. Continued growth in CO2 emissions over this century and beyond would lead to an atmospheric concentration not experienced in tens to hundreds of millions of years. There is broad consensus that the further and the faster the Earth system is pushed towards warming, the greater the risk of unanticipated changes and impacts, some of which are potentially large and irreversible.
In 2014 and 2015, emission growth rates slowed as economic growth became less carbon-intensive. Even if this slowing trend continues, however, it is not yet at a rate that would limit global average temperature change to well below 3.6°F (2°C) above preindustrial levels.
Fahey encourages everyone to read the summary, and to share the report.
Which I am doing here.
- Donald J. Wuebbles, David W. Fahey, Kathy A. Hibbard, David J. Dokken, Brooke C. Stewart, and Thomas K. Maycock, Climate Science Special Report: Fourth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, 2017. https://science2017.globalchange.gov/