The Fourth National Climate Assessment (NCA4) report has been published, and it's filled with the kind of fairly grim news you've probably come to expect by now. The comprehensive report is the culmination of decades of environmental research by scientists from 13 federal agencies, and outlines the findings of ongoing climate studies, how the changes will affect the environment, society and the economy, and what we should be doing about it.

The report comes out of the US Global Change Research Program (USGCRP), which was mandated by Congress in the 1990s to research the changing planet and present its findings to Congress and the US President every four years. The publishing of the report was led by the NOAA and compiled by experts at 13 federal member agencies, including NASA, the EPA, the Smithsonian, the National Science Foundation, US AID, and the Departments of Defense, Energy, Agriculture, Commerce, Health & Human Services, the Interior, State and Transportation.

This iteration of the report focuses on the human welfare, societal and environmental impacts of climate change. It takes into account observed and projected risks, and examines how different mitigation strategies might work to reduce the worst outcomes – as well as what might happen if we don't do anything. The aim is help inform political decision-makers, utility and natural resource managers, public health officials, emergency planners and the general public.

So what does the report actually say? Here are a few of the "highlights."

National Climate Assessment

The assessment's introduction doesn't mince words: "Earth's climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities," it reads. The effects are already apparent in the form of more extreme weather – examples include ongoing droughts, the intense 2017 hurricane season and the most destructive wildfire season on record in California.

The report projects that annual average temperatures in the US will continue to rise, regardless of our mitigation efforts. The best-case scenario says that by late this century temperatures will increase by at least 2.3° F (1.3° C) compared to averages between 1986 and 2015. If carbon emissions continue to increase unabated, the report predicts temperature increases of between 5.4° and 11° F (3° and 6.1° C), with devastating consequences.

While the report acknowledges that the US and other countries are beginning to respond in ways that might protect us and future generations from the worst effects of climate change, these measures don't "currently approach the scales needed to avoid substantial damages to the US economy, environment, and human health and well-being over the coming decades."

The report states that clean air and water, crop pollination, and wood and fiber production will be degraded as a result of an increase in wildfires, coastal floods, a loss of important native species and outbreaks of insects and disease.

Perhaps one of the most worrying trends is water availability. Rising air and water temperatures are changing cycles of rain and snow, which results in intense droughts broken only by heavy, short-lived downpours. Rather than providing relief, those intermittent downpours can cause flash flooding and degrade the quality of surface water. Shortages would be devastating beyond the obvious issue of drinking water – energy production is under threat too, since water is key for hydropower and cooling systems in other power plants.

Crop yields and livestock health are expected to decline across the board, as a result of lower water availability, and increases in temperature, soil erosion, and outbreaks of disease and pests. That in turn could lead to nationwide food shortages, price increases and economic hardship for rural communities.

All of this is expected to affect human health in a number of ways. Disease outbreaks will likely rise, spread through poorer-quality food and water and disease-carrying insects venturing further afield. Deaths due to hotter weather are projected to rise, and allergies like asthma and hay fever are expected to become more frequent and severe.

More extreme weather and rising sea levels are also projected to affect energy and transportation systems, buildings, infrastructure and industry. Bridges, roads and pipelines could be at risk due to heavy rainfall and higher tides, and the already-aging infrastructure doesn't seem ready to cope with the changes.

Buried on Black Friday

The report says that these issues are being fought on many fronts, but the only way to prevent the worst-case scenarios from materializing is to drastically reduce carbon dioxide emissions. The Paris Agreement outlined how to do this, and set a target of keeping global temperatures from rising more than 3.6° F (2° C). But in June 2017, US President Donald Trump infamously pulled out of the agreement.

In keeping with that mindset, the White House quietly released this National Climate Assessment on the afternoon of Black Friday, apparently hoping that the Thanksgiving hangover and shopping frenzy would be enough of a distraction. Even stranger is the fact that the release of this report was suddenly brought forward by two weeks, apparently surprising even its authors.

Besides the schedule shake-up, the scientists behind the project say that the findings at least have been published transparently. That isn't necessarily a given with the current administration, which is not shy about debating the science of climate change.

"Decisions that decrease or increase emissions over the next few decades will set into motion the degree of impacts that will likely last throughout the rest of this century, with some impacts (such as sea level rise) lasting for thousands of years or even longer," the report says. "Early and substantial mitigation offers a greater chance for achieving a long-term goal, whereas delayed and potentially much steeper emissions reductions jeopardize achieving any long-term goal."

That makes this assessment particularly interesting. While Trump and co. were content to condemn a similarly-bleak report from the Intergovernmental Panel on Climate Change (IPCC) recently, that's in line with their vilification of the United Nations. This National Climate Assessment, backed by science and observations from 13 federal agencies within the US government, might be harder to ignore.

Read the report in full at the NCA Global Change website.

Source: NOAA