Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Earth sunblock only needed if planet warms easily

12.10.2012
Planet's sensitivity to greenhouse gases will determine how much shading could be needed to slow temperature rise
An increasing number of scientists are studying ways to temporarily reduce the amount of sunlight reaching the earth to potentially stave off some of the worst effects of climate change. Because these sunlight reduction methods would only temporarily reduce temperatures, do nothing for the health of the oceans and affect different regions unevenly, researchers do not see it as a permanent fix. Most theoretical studies have examined this strategy by itself, in the absence of looking at simultaneous attempts to reduce emissions.

Now, a new computer analysis of future climate change that considers emissions reductions together with sunlight reduction shows that such drastic steps to cool the earth would only be necessary if the planet heats up easily with added greenhouse gases. The analysis, reported in the journal Climatic Change, might help future policymakers plan for a changing climate.

The study by researchers at the Department of Energy's Pacific Northwest National Laboratory explored sunlight reduction methods, or solar radiation management, in a computer model that followed emissions' effect on climate. The analysis shows there is a fundamental connection between the need for emissions reductions and the potential need for some sort of solar dimming.

"It's a what-if scenario analysis," said Steven Smith with the Joint Global Change Research Institute in College Park, Md,, a joint venture between PNNL and the University of Maryland. "The conditions under which policymakers might want to manage the amount of sun reaching earth depends on how sensitive the climate is to atmospheric greenhouse gases, and we just don't know that yet."

The analysis started with computer-based virtual worlds, or scenarios, that describe different potential pathways to reduce greenhouse gas emissions, which limits the amount of heat in the earth system due to greenhouse gas accumulation. The researchers combined these scenarios with solar radiation management, a type of geoengineering method that might include shading the earth from the sun's heat by either brightening clouds, mimicking the atmospheric cooling from volcanic eruptions or putting mirrors in space.

"Solar radiation management doesn't eliminate the need to reduce emissions. We do not want to dim sunlight over the long term — that doesn't address the root cause of the problem and might also have negative regional effects. This study shows that the same conditions that would call for solar radiation management also require substantial emission reductions in order to meet the climate goals set by the world community," said Smith.

How much sun blocking might be needed depends on an uncertain factor called climate sensitivity. Much like beachgoers in the summer, the earth might be very sensitive to carbon dioxide, like someone who burns easily and constantly slathers on the sunscreen, or not, like someone who can get away with SPF 5 or 10.

Scientists measure climate sensitivity by how many degrees the atmosphere warms up if the concentration of carbon dioxide doubles. Smith said if the climate has a medium sensitivity of about 3 degrees Celsius (5.4 degrees Fahrenheit) per doubling of carbon dioxide, "it's less likely we'd need solar radiation management at all. We'd have time to stabilize the climate if we get going on reducing emissions. But if it's highly sensitive, say 4.5 degrees Celsius (8.1 degrees Fahrenheit) per doubling, we're going to need to use solar radiation management if we want to limit temperature changes."

According to NOAA's August report, the earth's temperature has already risen about 0.62 degrees Celsius (1.12 degrees Fahrenheit) since the beginning of the 20th century as the carbon dioxide in the atmosphere has grown from 290 parts per million to 379 parts per million.

But the atmosphere hasn't reached equilibrium yet — even if humans stopped putting more carbon dioxide into the air, the climate would still continue to change for a while longer. Scientists do not know what temperature the earth will reach at equilibrium, because they don't know how sensitive the planet is to greenhouse gases.

Further, the study showed that, when coupled with emission reductions, the amount of solar radiation management needed could be far less than the amount generally considered by researchers so far.

"Much of the current research has examined solar radiation management that is used as the sole means of offsetting a doubling of carbon dioxide concentrations. What we showed is that when coupled with emissions reductions, only a fraction of that amount of 'solar dimming' will be needed. This means that potential adverse impacts would be that much lower," said Smith. "This is all still in the research phase. We do not know enough about the impacts of potential solar radiation management technologies to use them at this time."

The study will also help decision-makers evaluate solar reduction technologies side-by-side, if it comes to that. Smith and his coauthor, PNNL atmospheric scientist and Laboratory Fellow Phil Rasch, devised a metric to quantify how much solar radiation management will be needed to keep warming under a particular temperature change threshold. Called degree-years, this metric can be used to evaluate the need for potential sunlight dimming technologies.

Whether such technologies will be needed at all, time will tell.

This work was supported by the non-profit Fund for Innovative Climate and Energy Research.

Reference: Steven J. Smith and Philip J. Rasch, 2012. The Long-Term Policy 1 Context for Solar Radiation Management, Climatic Change, doi: 10.1007/s10584-012-0577-3. (http://www.springerlink.com/content/31674q46k61p86h7/)


The Joint Global Change Research Institute is a unique partnership formed in 2001 between the Department of Energy's Pacific Northwest National Laboratory and the University of Maryland. The PNNL staff associated with the center is world renowned for expertise in energy conservation and understanding of the interactions between climate, energy production and use, economic activity and the environment.

Mary Beckman | EurekAlert!
Further information:
http://www.pnnl.gov

More articles from Earth Sciences:

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

nachricht Modeling magma to find copper
13.01.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>