More severe, more frequent, longer lasting:
Powerful Heat Waves in Earth's Future

Big Bear Solar Observatory image of the Sun
The Sun in 2004 was photographed by the Big Bear Solar Observatory in Big Bear Lake, California, operated by the New Jersey Institute of Technology.

The observatory sits out in the middle of the lake to reduce distortion from Sun heating the air above the ground. Turbulence is reduced by a smooth flow of wind across the lake. The usually cloudless skies over the lake and the clear air at 6,750 feet elevation make the observatory a great site for solar observations.

The observatory was built by California Institute of Technology in 1969. NJIT took over management in 1997. It is funded by NASA, the National Science Foundation, the U.S. Air Force and Navy, and other agencies.

Click to enlarge the image.
Heat waves in Chicago, Paris, and elsewhere in North America and Europe will become more intense, more frequent, and longer lasting in the 21st century, according to a 2004 study by scientists at the National Center for Atmospheric Research (NCAR).

In the United States, the increase in heat wave severity will be greatest in the West and the South.

Already starting. The study found an increase in heat-absorbing greenhouse gases intensifying an unusual atmospheric circulation pattern already observed during heat waves in Europe and North America.

As the pattern becomes more pronounced, severe heat waves could occur in the Mediterranean region and the southern and western United States. Other parts of France, Germany, and the Balkans also could become more susceptible to severe heat waves, NCAR reported.

Hotter globe. Later,NCAR scientists reported that global warming had produced half of the extra hurricane-fueled warmth in the North Atlantic in 2005, while natural cycles accounted for only a small part.

Leading climatologists reported to the U.S. Congress in 2006 that Earth is heating up and human activities are responsible for much of the recent warming. They found average global surface temperatures in the Northern Hemisphere went up about 1 degree during the 20th century.

Hottest in centuries. In 2006, the National Academy of Sciences announced its conclusion that the recent warming of Earth is as bad as it's been for 400 years. In fact, it may have been as many as 2,000 years since Earth has been so hot.

Historical perspective. For almost 19 centuries, between 1 A.D. and 1850, fluctuations of the Sun and erupting volcanos were the main sources of greenhouse gases in the atmosphere, according to scientists. Temperature changes then were much less pronounced than the recent noticeable warming attributed to increases in the levels of greenhouse gases in the atmosphere since the mid-19th century.

Two greenhouse gases – methane and carbon dioxide – have been blamed for retaining heat in the atmosphere. Scientists found the levels of those two remained mostly level for 12,000 years, but then underwent a big increase in the 20th century.

Earth did experience relatively warm conditions around the year 1000. That was followed by a so-called Little Ice Age from around 1500 to 1850.

Who's doing the research? NCAR is a federally funded research and development lab exploring Earth's atmosphere and its interactions with the Sun, the oceans, the biosphere and human society. It is operated by the University Corporation for Atmospheric Research (UCAR) under the sponsorship of universities and the National Science Foundation (NSF), the U.S. Department of Energy (DOE), and other agencies. NSF is an independent agency of the federal government established to promote the progress of science. The National Academy of Sciences (NAS) is a private institution approved by Congress to advise the government about science. The 2006 report was published by the American Geophysical Union (AGU), a nonprofit organization of more than 40,000 geophysicists in 130 countries.

Projections of the 2004 NCAR study:

Killer heat. Heat waves can kill more people in a shorter time than almost any other climate event. The study compared the years 1961-1990 with the future years 2080-2099 to determine how greenhouse gases and sulfate aerosols might affect future climate in Europe and the United States, focusing on Paris and Chicago. They assumed there would not be much political policy intervention to slow the buildup of greenhouse gases.

Clear skies, prolonged heat. During the Paris and Chicago heat waves, changes in atmospheric pressure produced clear skies and prolonged hot conditions at the surface.

In the study model, similar atmospheric pressure changes are enhanced during heat waves in both regions as carbon dioxide accumulates in the atmosphere.

More severe. The scientific model showed heat waves would become more severe.

During the 1995 Chicago heat wave, the most severe health impacts resulted from the lack of cooling relief several nights in a row, according to health experts.

In the model, the worst three-day heat waves show a rise of more than 5.4 degrees Fahrenheit in minimum nighttime temperatures in the western and southern United States and the Mediterranean region of Europe.

More often. They will occur more often. The average number of heat waves in the Chicago area would increase in the coming century by 25 percent, from 1.66 per year to 2.08. In Paris, the average number would increase 31 percent, from 1.64 per year to 2.15.

Last longer. They will last longer. Chicago's present heat waves range from 5.39 to 8.85 days. Future events would increase to between 8.5 and 9.24 days.

For Paris, present-day heat waves range from 8.33 to 12.69 days. In the future decades, they would stretch to between 11.39 and 17.04 days.

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