Climate Science Special Report
The following is taken almost verbatim from the U.S. Global Change Research Program website. I provide it here, so you may see the most current federal government assessment of the science behind climate change as it pertains to the United States.
Scroll down to the Highlights Section to get a more concise assessment of the situation we are facing as a nation.
For a global assessment, one would have to view the Intergovernmental Panel on Climate Change (IPCC)’s website, the leading international body for the assessment of climate change. The most current assessment is the Fifth Assessment Report, which was released in four parts between September 2013 and November 2014. The IPCC is currently in its Sixth Assessment cycle, which will be completed in 2021.
The U.S. Global Change Research Program (USGCRP) was established by Presidential Initiative in 1989 and mandated by Congress in the Global Change Research Act (GCRA) of 1990 to “assist the Nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change.”
USGCRP is steered by the Subcommittee on Global Change Research (SGCR) of the National Science and Technology Council, which is overseen by the White House Office of Science and Technology Policy (OSTP).
The Climate Science Special Report, USGCRP’s Fourth National Climate Assessment | Volume I was published in 2017. The report is an authoritative assessment of the science of climate change, with a focus on the United States. It represents the first of two volumes of the Fourth National Climate Assessment, mandated by the Global Change Research Act of 1990. Report downloads can be accessed on this link.
Highlights of the Climate Science Special Report:
- Global annually averaged surface air temperature has increased by about 1.8°F (1.0°C) over the last 115 years (1901–2016). This period is now the warmest in the history of modern civilization. The last few years have also seen record-breaking, climate-related weather extremes, and the last three years have been the warmest years on record for the globe. These trends are expected to continue over climate timescales.
- This assessment concludes, based on extensive evidence, that 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. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.
- In addition to warming, many other aspects of global climate are changing, primarily in response to human activities. 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.
- For example, 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. Human-caused climate change has made a substantial contribution to this rise since 1900, contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years. 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. Sea level rise will be higher than the global average on the East and Gulf Coasts of the United States.
- Changes in the characteristics of extreme events are particularly important for human safety, infrastructure, agriculture, water quality and quantity, and natural ecosystems. Heavy rainfall is increasing in intensity and frequency across the United States and globally and is expected to continue to increase. The largest observed changes in the United States have occurred in the Northeast.
- Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent. Recent record-setting hot years are projected to become common in the near future for the United States, as annual average temperatures continue to rise. Annual average temperature over the contiguous United States has increased by 1.8°F (1.0°C) for the period 1901–2016; 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 in those regions as the climate changes, with profound changes to regional ecosystems.
- Annual trends toward earlier spring melt and reduced snowpack are already affecting water re- sources in the western United States and these trends are expected to continue. Under higher scenarios, and assuming no change to current water resources management, chronic, long-duration hydro- logical 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. Without major reductions in emissions, the increase in annual average global temperature relative to preindustrial times could reach 9°F (5°C) or more by the end of this century. 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.
- The observed increase in carbon emissions over the past 15–20 years has been consistent with higher emissions pathways. 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.
According to a recent press release, “The (NCA4) Vol. II remains on track for a December delivery in fulfillment of the Congressional mandate. Authors have been revising chapters and responding to comments submitted in the final round of review by USGCRP member agencies in May and June. The responses and revisions will be reviewed by the NCA4 Vol. II Federal Steering Committee to ensure all comments have been adequately addressed. Authors continue to finalize graphics and complete the appropriate metadata in an effort to provide an unprecedented level of traceability and transparency for a federal climate assessment through the Global Change Information System.”
It is unknown at this time if politics has creeped into NCA4 Volume II of the Report. Here is an article from Earth & Space Science News from November 6, 2017 assessing why the White House released Volume I of the Report, which differs from the administration’s stance, without political tampering.
Time will tell.