Don’t know what to think about climate change?

President Trump says, “Something’s changing and it’ll change back again.” The UN says that Earth has 10 years to avert climate change catastrophe. Who should you believe? How about the U.S. government? Thirteen federal departments including the Departments of Agriculture, Commerce, Defense, Energy, Health and Human Services, Interior, State, Transportation, and several science agencies collaborated on the Fourth National Climate Assessment. Here is what they say: Global air temperature has increased by 1.8 degrees Fahrenheit over the last 115 years. This period is now the warmest in the history of modern civilization. It is extremely likely that human activities, especially greenhouse gas emissions, are the dominant cause of the observed warming since 1950. The report states that there is no convincing alternative explanation.

Changes such as increases in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; and increasing atmospheric water vapor have been observed worldwide. Of particular concern for the Pacific Northwest is ocean acidification resulting from the absorption of atmospheric carbon dioxide. Acidic water dissolves carbonate shells, making it increasingly difficult for shellfish, shrimp, crab and corals to survive. Since 1800, ocean water has become 30 percent more acidic - faster than any known change in ocean chemistry in the last 50 million years.

Global sea level has risen 7 to 8 inches since 1900, with almost half of that rise occurring since 1993. The rate of rise is greater than during any preceding century in at least 2,800 years. Sea level rise has already affected the U.S. The incidence of daily tidal flooding is accelerating in more than 25 Atlantic and Gulf Coast cities. Sea levels will continue to rise - by at least several inches in the next 15 years and by 1 to 4 feet by 2100. A rise of as much as 8 feet by 2100 cannot be ruled out. If all the ice covering Antarctica, Greenland, and mountain glaciers melt, sea level would rise about 265 feet.

Heavy rainfall, increasing in intensity and frequency across the U.S., is expected to continue to increase. Heatwaves have become more frequent in the U.S. 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, as temperatures continue to rise. The incidence of large forest fires in the western U.S. and Alaska has increased since the early 1980s and is projected to further increase.

Future temperature increases will depend on the amount of greenhouse gases emitted globally. Without major reductions, the increase in global temperature could reach 9 degrees F or more by 2100. With significant reductions in emissions, the increase in global temperature could be limited to 3.6 degrees F or less.

Now is the time to get involved. Inform yourself, share concerns with your neighbors, join organizations such as Local 20/20, and advocate for action at all levels. It’s not yet too late!

Thomas Engel is a retired UW chemistry professor, serves on the PUD Citizen Advisory Board, and is moderatorof Local 20/20 Energy Action Group.