Congress requires the federal government to produce every four years the National Climate Assessment. The report amounts to the best scientific evaluation the country can make about climate change. The first volume of the latest assessment arrived in May. The second was released on Friday, and it contained this arresting conclusion: “The assumption that current and future climate conditions will resemble the past is no longer valid.”

This peer-reviewed assessment reflects the work of 13 federal agencies and roughly 300 scientists. It serves as a timely complement to the recent report from the U.N. Intergovernmental Panel on Climate Change in its precision and straight talk. It makes plain the fallout already is here — with more severe consequences coming sooner than many expect.

For those tempted to argue the scientists are alarmists, note the past 30 years. Their projections have been right about climate change.

Hard to miss in the second volume of the assessment is the forecast for Ohio and nearby states without more aggressive efforts to slow emissions of carbon dioxide and other greenhouse gases. The region steadily will be warmer, wetter and more humid. A crucial part of the regional economy, farming will be hit hard, in the form of such things as pests and crop disease, the health of livestock and yields at risk. The assessment projects that on the current track, agricultural production by 2050 in this part of the country will decline to levels last seen during the economic downturn of the 1980s.

In all, the consequences will take varied shape. Lower yields will ripple through markets. Heavy rains will drive increased runoff into Lake Erie, inviting expanded algal blooms. Flooding will strain public works, the $1.2 billion makeover of the Akron combined sewer system all the more necessary. In some instances, the reliability of water supplies will be jeopardized.

Even manufacturing supply chains would see the effect. Manufacturing is a more global operation today. Thus, calamities elsewhere lead to disruptions closer to home. The assessment calculates that since 2015, the American economy has suffered $400 billion in losses due to climate change. It projects that by century’s end, the economy will contract by as much as 10 percent if adequate steps are not taken to deal with the warming planet.

The harmful fallout extends to public health, higher temperatures fueling smog and accelerating the number of premature deaths.

The contrast hardly could be more apparent, or troubling, such projections arriving as the Trump White House retreats from efforts to reduce greenhouse emissions, opposing its predecessor’s limits on tailpipe and power plant pollution. The president wants to withdraw from the Paris climate agreement and see a revival of the coal industry. One virtue of the assessment is that evidence in such detail likely will make more difficult the president’s case for easing regulations.

The assessment amounts to another powerful argument for acting swiftly to address climate change. It also outlines where to move forward, applying a price to greenhouse emissions, imposing government regulations to limit those emissions and investing in research to develop clean energy technologies. This has been the recommended path for decades. Unfortunately, it has yet to be followed. The hope is that in their increasingly stronger words, data and understanding, scientists will prevail sooner. Again, the country has been warned.