White House Report: Climate Change Is Already Here, and Is Going to Get Worse

The colors on the map show temperature changes over the past 22 years (1991-2012) compared to the 1901-1960 average, and compared to the 1951-1980 average for Alaska and Hawai‘i. NOAA NCDC / CICS-NC

Climate change "has moved firmly into the present," opens a congressionally mandated report released Tuesday on the state of climate change in the U.S. Popularly imagined as affecting faraway corners of the Earth, less fortunate than ours, climate change is in fact already being felt all over the U.S., and it is bound to get worse, the report says. Water is growing scarcer, heat waves are happening more often and are more severe, torrential downpours are more common, and wildfires are getting worse. The 2014 National Climate Assessment, written by 300 climate experts and reviewed by the National Academy of Sciences, paints a dire picture.

Already, "summers are longer and hotter, and extended periods of unusual heat last longer than any living American has ever experienced," the report found. "Winters are generally shorter and warmer. Rain comes in heavier downpours. People are seeing changes in the length and severity of seasonal allergies, the plant varieties that thrive in their gardens, and the kinds of birds they see in any particular month in their neighborhoods."

In coastal cities and those near large rivers, the streets flood more regularly during storms and high tides than they in the past. "Insurance rates are rising in some vulnerable locations, and insurance is no longer available in others," according to the report.

"Americans face choices," the report warns: Reduce emissions and develop adaptation methods, or face extreme consequences. By 2100, even if the U.S. substantially cuts emissions, the average temperature is projected to rise by 3 to 5 degrees Fahrenheit (referred to in the below charts as the "B1 scenario"). In a do-nothing scenario, in which emissions continue to increase at the rate they are now, temperatures are set to rise by 5 to 10 degrees (referred to as the "A2 scenario").

In a do-nothing scenario, temperatures could rise as much as 10 degrees by 2100.

Dramatic reduction in emissions would, for example, stave off the unimaginably punishing heat waves. In a do-nothing scenario, where emissions continue to increase at the rate they are now, the hottest days will be "about 10 to 15 degrees hotter" by the end of the century. That means those once-in-20-years-105-degree days will, in the next 60 to 80 years, become 115- to 120-degree days.

Heat waves are set to become far more severe.

The rise in extreme heat would not just be dangerous to health—it would cause a massive drop in soil moisture, which is a key indicator of drought. That in turn would wreak havoc on our food and water supply.

Projected changes in soil moisture by the end of the century.

Another dramatic shift is the uptick in the frequency of torrential downpours. When heat rises, and more water evaporates from the warming surface of the ocean, that excess moisture eventually makes landfall as rain or snow. Already, amid rising temperatures, "heavy downpours are increasing nationally, especially over the last three to five decades," according to the report. The proportion of precipitation that falls in very heavy rain events has spiked a whopping 71 percent in the Northeast over the past 50 years. The Midwest has seen a 37 percent rise, and that proportion has risen by 27 percent in the South.

The map shows percent increases in the amount of precipitation falling in major downpour events (the heaviest 1% of all rain events) from 1958 to 2012.
The top two maps show projected changes in the average amount of precipitation falling on the wettest day of the year at the end of the century. The two maps on the bottom show projected changes in the number of consecutive dry days per year.

While the report highlights downpours, it also says droughts will increase. Already, local areas are competing for water from "stressed" regional waters supplies. In general, watersheds are considered stressed when water demand from agriculture, power plants, and the local community exceeds 40 percent of available supply, but many basins experience "critical stresses" long before they reach that threshold, according to the report. The map below, compiled from 2011 data, shows widespread water stress is already afflicting much of the Southwest, western Great Plains and parts of the Northwest. Rising temperatures due to climate change will increase evaporation, thus significantly increasing water demand across most of the United States.

Climate change is already putting significant stress on U.S. water supplies.

In 1990, Congress ordered that a major report on climate change be compiled every four years, according to The New York Times. Presidents Bill Clinton and George W. Bush, however, were sluggish to comply, and this report is only the third to have been published since then. President Barack Obama plans to do a series of media events and interviews with television meteorologists this week in an effort to amplify the report's findings, and the report is expected to be highlighted when he proposes the next phase of emissions cuts for existing power plants this June.