Researchers predict that global warming generally will make summers hotter and winters milder from Southern California to the northeastern United States to parts of Africa, Asia and Latin America.

The impact will vary depending on different regions of the planet, according to a report published Wednesday by the National Oceanic and Atmospheric Administration, or NOAA.

While the U.S., Canada and northern Europe are expected to see modest increases in mild to hot days, people living in the tropics should brace for significantly more heat, said authors of the study, which appears in the journal Climatic Change.

“We looked at mild weather in the hopes of making climate change more relatable to normal people,” said Karin van der Wiel, a researcher at Princeton University working with NOAA. “Maybe it will get them thinking about it more.”


Mild days are defined in the study as those with a daily maximum temperature between 64 and 86 degrees Fahrenheit, with a half-inch of rain or less and limited humidity.

The current global average of such pleasant weather days is 74 per year, a number that’s projected to drop by four during the next two decades and 10 by the end of this century.

People living in certain areas of Africa, Asia and Latin America could lose from 15 up to as many as 50 of these mild days a year by century’s end, according to the report.

Surfers put on their wetsuits before entering the water at Powerhouse Park in Del Mar. (Union-Tribune file photo )


At the same time, San Diegans could see a net increase in the number of days suitable for jogging or riding a bike — although fewer such mild days will occur during the summer.

San Diego County currently has 180 mild days per year on average, the researchers said. By 2035, the report said, San Diegans will likely experience an average of six fewer mild days between June and August, but will probably have an increase of just as many such days in the winter.

By the end of the century, San Diego is expected to have a net average increase of three mild days each year.

Los Angeles County, which currently has an average of 157 mild days a year, is expected to lose four such days between June and August, but break even with gains during winter months. By 2100, the region would add an average of six more pleasant weather days overall.


While scientists have struggled to predict the near-term impacts of global warming on events such as hurricanes, drought and wildfires, increases in average temperatures are considered to have a more straightforward relationship with climate change.

Unlike a daily weather forecast, these yearly temperature predictions are averaged over decades to increase accuracy.

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