Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Daily record high temperatures occurred twice as often as record lows over past decade

13.11.2009
Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows.

The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb.

"Climate change is making itself felt in terms of day-to-day weather in the United States," says Gerald Meehl, a researcher at the National Center for Atmospheric Research (NCAR) and the lead author of the study. "The ways these records are being broken show how our climate is already shifting."

The study, by authors at NCAR, Climate Central, The Weather Channel, and the National Oceanic and Atmospheric Administration (NOAA), has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union (AGU).

If temperatures were not warming, the number of record daily highs and lows being set each year would be approximately even.

Instead, for the period from January 1, 2000, to September 30, 2009, the continental United States set 291,237 record highs and 142,420 record lows, as the country experienced unusually mild winter weather and intense summer heat waves.

A record daily high means that temperatures were warmer on a given day than on that same date throughout a weather station's history.

The authors used a quality control process to ensure the reliability of data from thousands of weather stations across the country, while looking at data over the past six decades to capture longer-term trends.

This decade's warming was more pronounced in the western United States, where the ratio was more than two to one, than in the eastern United States, where the ratio was about one-and-a-half to one.

The study also found that the two-to-one ratio across the country as a whole could be attributed more to a comparatively small number of record lows than to a large number of record highs.

This indicates that much of the nation's warming is occurring at night, when temperatures are dipping less often to record lows.

This finding is consistent with years of climate model research showing that higher overnight lows should be expected with climate change.

In addition to surveying actual temperatures in recent decades, Meehl and his co-authors turned to a sophisticated computer model of global climate to determine how record high and low temperatures are likely to change during the course of this century.

The modeling results indicate that, if nations continue to increase their emissions of greenhouse gases in a "business as usual" scenario, the U.S. ratio of daily record high to record low temperatures would increase to about 20-to-1 by mid-century and 50-to-1 by 2100.

The mid-century ratio could be much higher if emissions rose at an even greater pace, or it could be about 8-to-1 if emissions were reduced significantly, the model showed.
The authors caution that such predictions are, by their nature, inexact.
Climate models are not designed to capture record daily highs and lows with precision, and it remains impossible to know future human actions that will determine the level of future greenhouse gas emissions.

The model used for the study, the NCAR-based Community Climate System Model, correctly captured the trend toward warmer average temperatures and the greater warming in the West, but overstated the ratio of record highs to record lows in recent years.

However, the model results are important because they show that, in all likely scenarios of future greenhouse gas emissions, record daily highs should increasingly outpace record lows over time.

"If the climate weren't changing, you would expect the number of temperature records to diminish significantly over time," says Claudia Tebaldi, a statistician with Climate Central who is one of the paper's co-authors.

"As you measure the high and low daily temperatures each year, it normally becomes more difficult to break a record after a number of years. But as the average temperatures continue to rise this century, we will keep setting more record highs."

The study team focused on weather stations that have been operating since 1950. They found that the ratio of record daily high to record daily low temperatures slightly exceeded one to one in the 1950s, dipped below that level in the 1960s and 1970s, and has risen since the 1980s.

The results reflect changes in U.S. average temperatures, which rose in the 1950s, stabilized in the 1960s, and then began a warming trend in the late 1970s.

Even in the first nine months of this year, when the United States cooled somewhat after a string of unusually warm years, the ratio of record daily high to record daily low temperatures was more than three to two.

Despite the increasing number of record highs, there will still be occasional periods of record cold, Meehl notes.

"One of the messages of this study is, you still get cold days," Meehl says. "Winter still comes. Even in a much warmer climate, we're setting record low minimum temperatures on a few days each year. But the odds are shifting so there's a much better chance of daily record highs instead of lows."

The study team analyzed several million daily high and low temperature readings taken over the span of six decades at about 1,800 weather stations across the country, thereby ensuring ample data for statistically significant results.

The readings, collected at the National Oceanic and Atmospheric Administration's National Climatic Data Center, undergo a quality control process at the data center that looks for such potential problems as missing data as well as inconsistent readings caused by changes in thermometers, station locations, or other factors.

Meehl and his colleagues then used temperature simulations from the Community Climate System Model to compute daily record highs and lows under current and future atmospheric concentrations of greenhouse gases.

The study was funded by the National Science Foundation (NSF), NCAR's sponsor, and by the Department of Energy and Climate Central.

Title:
"The relative increase of record high maximum temperatures compared to record low minimum temperatures in the U.S.""
Authors:
Gerald A. Meehl and Larry McDaniel: National Center for Atmospheric Research+, Boulder, CO, USA;

Claudia Tebaldi: Climate Central, Princeton, N.J., USA;

Guy Walton: The Weather Channel, Atlanta, GA, USA;

David Easterling: National Climate Data Center, Asheville, NC, USA.

Contact information for the authors:
Gerald Meehl, NCAR Scientist. Tel: +1 (303) 497-1331, email:
meehl@ncar.ucar.edu

Peter Weiss | American Geophysical Union
Further information:
http://www.agu.org

More articles from Earth Sciences:

nachricht Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation

nachricht Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>