Climate Research

More moisture in the air due to a warmer atmosphere fueled by increased greenhouse gas emissions will make extreme precipitation events more intense. That’s according to a NOAA-led study published in Geophysical Research Letters.

The study also finds that if carbon dioxide levels continue to rise at a high emission rate, we can expect a 20 – 30 percent increase in the maximum precipitation possible in large sections of the Northern Hemisphere by the end of this century.

This Week in Climate News

Winter Is Finally Releasing Its
Chilly Grip on the U.S.

Clouds Helped Enhance Greenland’s Record Melting

U.S. Dominated Global Disaster Losses in 2012: Swiss Re

The Archives

Click here to see past issues for each participating market.

Tweetable Fact

Data shows that in the area, spring leaf-out has arrived on avg since 1982


MAP: How spring leaf-out, a sign that winter is finally over, has varied on avg. across the U.S.

For More Information

Contact Us:

Click here for a high-resolution version

The time when leaves start turning green is one sign that winter is finally over, and spring is here to stay.

But the date that trees turn green changes every year, and depends a lot on temperature. A warm spring can cause leaves to bloom earlier than normal, while a cold spring can let winter cling to the forests for few more drab weeks.

However, the story gets more complicated than that. A spring that gets too warm too quickly can actually delay the process, since the mild temperatures can leave the trees vulnerable to a late-winter freeze. Similarly, if the entire winter is warmer than average, then trees that require a certain amount of “winter chilling” to bloom on time, may also be delayed in the spring.

The map above shows trends in the date when entire forests starting turning green, over the 26-year period from 1982-2008. The data comes from satellite observations of the overall color of the forest. This is a rough measurement, but it allows scientists to make judgments about ecosystems and climate at a broad scale.

The map shows that leaves are coming earlier in some parts of the country like the Rocky Mountains and Appalachians, but that spring leaf-out has been delayed over time in parts of the Southeast, Northeast and Midwest. This is consistent with climate research that shows that many types of plants have not been blooming uniformly earlier over time.

We looked at the difference between when this time arrived during the first five years and the last five years of the study. In the area, this date is coming about on average since 1982.

Rising temperatures may actually be behind the way this date shifts in both directions. New research suggests that the response of spring leaves to warming temperatures may not be linear, due to the effects of reduced winter chilling, and increased vulnerability to late-winter freezes.

A continuing trend of warming winters may lead to further changes in the familiar timing of the seasons.

Unsubscribe from this list