Climate change will bring more and more extreme precipitation events this century.
A new study from NOAA’s National Climatic Data Center confirms what climate scientists have long been saying about climate change’s effect on the hydrological cycle.
If you are not familiar with this term, you are certainly familiar with what it describes. As the sun warms the earth, water evaporates from oceans, lakes, and rivers, which then form clouds that produce rain and snow. More evaporation happens when the ocean and the air is warmer, which has been happening steadily for some time.
The NOAA study, published in Geophysical Research Letters, found that extreme precipitation events will become more intense this century as the globe continues to warm. Extra moisture expected from that warming will be the dominant factor fueling this increase in extreme precipitation, with a 20 to 30 percent more precipitation in the Northern Hemisphere by 2099.
The paper looked at three factors that go into the maximum precipitation value possible in any given location: moisture in the atmosphere, upward motion of air in the atmosphere, and horizontal winds. The team examined climate model data to understand how a continued course of high greenhouse gas emissions would influence the potential maximum precipitation. While greenhouse gas increases did not substantially change the maximum upward motion of the atmosphere or horizontal winds, the models did show a 20-30 percent increase in maximum moisture in the atmosphere, which led to a corresponding increase in the maximum precipitation value.
They looked at possible changes in winds that could offset increased water vapor, but found that those changes would be too small. We already know that specific events cannot be said to be directly caused by climate change, but as Kevin Trenberth puts it, “All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.” And we know that NOAA’s projections have already started to become the reality: a study in Nature found that several of the last decade’s extreme weather events would not have occurred without climate change.
The study’s authors hope that this will allow water managers, engineers, and infrastructure planners to better identify risks and mitigate potential disasters. National reports like this are valuable not only because funds for flood risk prevention studies are often attacked in Congress, but because climate impacts are often ignored, forcibly, at the state level. South Carolina buried an important report on climate impacts. North Carolina made it illegal to consider the latest climate science when preparing coastal regions for sea level rise.