Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

"Warming hole" delayed climate change over eastern United States

27.04.2012
50-year model suggests regional pollution obscured a global trend
Climate scientists at the Harvard School of Engineering and Applied Sciences (SEAS) have discovered that particulate pollution in the late 20th century created a "warming hole" over the eastern United States—that is, a cold patch where the effects of global warming were temporarily obscured.

While greenhouse gases like carbon dioxide and methane warm the Earth's surface, tiny particles in the air can have the reverse effect on regional scales.

"What we've shown is that particulate pollution over the eastern United States has delayed the warming that we would expect to see from increasing greenhouse gases," says lead author Eric Leibensperger (Ph.D. '11), who completed the work as a graduate student in applied physics at SEAS.

"For the sake of protecting human health and reducing acid rain, we've now cut the emissions that lead to particulate pollution," he adds, "but these cuts have caused the greenhouse warming in this region to ramp up to match the global trend."

At this point, most of the "catch-up" warming has already occurred.

The findings, published in the journal Atmospheric Chemistry and Physics, present a more complete picture of the processes that affect regional climate change. The work also carries significant implications for the future climate of industrial nations, like China, that have not yet implemented air quality regulations to the same extent as the United States.

Until the United States passed the Clean Air Act in 1970 and strengthened it in 1990, particulate pollution hung thick over the central and eastern states. Most of these particles in the atmosphere were made of sulfate, originating as sulfur emissions from coal-fired power plants. Compared to greenhouse gases, particulate pollution has a very short lifetime (about 1 week), so its distribution over the Earth is uneven.

"The primary driver of the warming hole is the aerosol pollution—these small particles," says Leibensperger. "What they do is reflect incoming sunlight, so we see a cooling effect at the surface."

This effect has been known for some time, but the new analysis demonstrates the strong impact that decreases in particulate pollution can have on regional climate.

The researchers found that interactions between clouds and particles amplified the cooling. Particles of pollution can act as nucleation sites for cloud droplets, which can in turn reflect even more sunlight than the particles would individually, leading to greater cooling at the surface.

The researchers' analysis is based on a combination of two complex models of Earth systems. The pollution data comes from the GEOS-Chem model, which was first developed at Harvard and, through a series of many updates, has since become an international standard for modeling pollution over time. The climate data comes from the general circulation model developed by NASA's Goddard Institute for Space Studies. Both models are rooted in decades' worth of observational data.

Since the early 20th century, global mean temperatures have risen—by approximately 0.8 degrees Celsius from 1906 to 2005—but in the U.S. "warming hole," temperatures decreased by as much as 1 degree Celsius during the period 1930–1990. U.S. particulate pollution peaked in 1980 and has since been reduced by about half. By 2010 the average cooling effect over the East had fallen to just 0.3 degrees Celsius.

"Such a large fraction of the sulfate has already been removed that we don’t have much more warming coming along due to further controls on sulfur emissions in the future," says principal investigator Daniel Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at SEAS.

Jacob is also a Professor of Earth and Planetary Sciences at Harvard and a faculty associate of the Harvard University Center for the Environment.

Besides confirming that particulate pollution plays a large role in affecting U.S. regional climate, the research emphasizes the importance of accounting for the climate impacts of particulates in future air quality policies.

"Something similar could happen in China, which is just beginning to tighten up its pollution standards," says co-author Loretta J. Mickley, a Senior Research Fellow in atmospheric chemistry at SEAS. "China could see significant climate change due to declining levels of particulate pollutants."

Sulfates are harmful to human health and can also cause acid rain, which damages ecosystems and erodes buildings.

"No one is suggesting that we should stop improving air quality, but it’s important to understand the consequences. Clearing the air could lead to regional warming," Mickley says.

Leibensperger, Jacob, and Mickley were joined by co-authors Wei-Ting Chen and John H. Seinfeld (California Institute of Technology); Athanasios Nenes (Georgia Institute of Technology); Peter J. Adams (Carnegie Mellon University); David G. Streets (Argonne National Laboratory); Naresh Kumar (Electric Power Research Institute); and David Rind (NASA Goddard Institute for Space Studies).

The research was supported by the Electric Power Research Institute (EPRI) and the U.S. Environmental Protection Agency (EPA); neither EPRI nor the EPA has officially endorsed the results. The work also benefited from resources provided by Academic Computing Services at SEAS.

Caroline Perry | EurekAlert!
Further information:
http://www.harvard.edu

More articles from Earth Sciences:

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

nachricht Canadian glaciers now major contributor to sea level change, UCI study shows
15.02.2017 | University of California - Irvine

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>