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A Better Answer to Climate Change Is Hidden in the Clouds

The views expressed are those of the author and are not necessarily those of Scientific American.


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Climate scientists are studying a bewildering array of changes taking place in the air, on land and in the sea. But where should they concentrate their efforts? First and foremost, it seems, are clouds. Better understanding of how clouds affect global warming, and how airborne particles affect cloud formation, is one of three gaps in knowledge that could most improve predictions of how extensively and quickly Earth’s climate will change.

So say three experts who played a major role in writing the latest climate assessment report published in late September by the Intergovernmental Panel on Climate Change (IPCC). They spoke as a group at the American Geophysical Union’s annual fall meeting being held this week in San Francisco. Considering that climate deniers are constantly accusing IPCC scientists of not having airtight data, it took some guts for the experts to identify gaps in knowledge. But they said the gaps do not undermine prevailing climate predictions, which have become increasingly thorough for two decades. Filling the gaps, they said, would further enhance the forecasts. In that sense, the experts are calling for scientists to do what scientists always strive to do: learn, then figure out what more needs to be discovered, and go find it.

The climate effect of clouds, especially low clouds, is still a bit of a mystery, said Olivier Boucher, from the Pierre Simon Laplace Institute in Paris, who was the lead author of the IPCC report chapter on clouds and aerosols (airborne particles). “Low-level clouds are the wild card” in many atmospheric models, he noted. And they are changing. For example, low clouds seem to be migrating toward the north and south poles, where they have less affect on blocking incoming heat from the sun and in absorbing heat radiated from the Earth. Scientists also do not have a good handle on whether low clouds are getting thicker, if they are holding more water vapor, or if the dwindling of Arctic sea ice is leading to more or less cloud formation.

A related gap in knowledge is how aerosols affect clouds. For example, black carbon—the particles emitted by burning fossil fuels—“is more important than we thought” in determining how much heat the atmosphere can trap, Boucher said. “It’s really critical to understand the feedbacks” that may occur between aerosols and clouds, and feedbacks between that interaction and changes in Arctic sea ice. Together, the set of feedbacks could substantially “amplify or dampen climate change,” Boucher said.

Those interactions feed into a second gap in understanding: how carbon is emitted, transported and stored among soils, plants, air and ocean—the so-called carbon cycle. Newly emitted carbon dioxide persists in the atmosphere for hundreds of years, so how readily it is absorbed and held in soil and seawater affects the extent of the greenhouse effect, as well as the now-rising acidity of ocean water, noted Philippe Ciais, also at the French institute and lead author of the IPCC chapter on biogeochemical cycles.

What’s happening in the ocean itself is a third gap that must be filled. Oceans absorb a large portion of the carbon dioxide emitted into the atmosphere. Although the top layer of the ocean has been warming somewhat in step with the air above it, that rate of warming may be slowing, even though CO2 emissions continue to increase worldwide. “Where is that heat going?” asked Dennis Hartmann from the University of Washington, author of the IPCC chapter on measurements of the Earth. Some scientists suspect that ocean currents are transporting that heat to deeper layers, but they just don’t know. A new, global system of buoys that can dive deep down into the water and rise over a series of days, again and again, should help generate an answer, Hartmann said.

A related question is whether the ocean is slowing the current rise of atmospheric temperatures, sometimes called the hiatus or the pause. More scientists are saying the pause may be driven by changes in the El Niño and La Niña cycle of ocean-atmosphere interactions in the central Pacific Ocean. If so, Hartmann asked, “How long will the hiatus persist?”

Other open questions, Hartmann said, are why Arctic sea ice is rapidly disappearing while Antarctic sea ice is increasing, where heavy rainfall is spreading, and how greater humidity in the atmosphere is affecting that rainfall as well as severe storms.

If scientists can fill these particular gaps in knowledge, Hartmann said, they should be able to predict not just long-term trends but changes on a decade-to-decade scale. That kind of fine-grained forecast would greatly help cities, municipalities, businesses, farmers and many others better plan ways to adapt to climate change.

The insight would help local weather forecasters, too. For example, atmospheric scientists can only reliably model cloud cover a few hours into the future, Boucher noted. “We would like to be able to do that for a month,” he said.

Photo courtesy of Yamato on WikimediaCommons

Mark Fischetti About the Author: Mark Fischetti is a senior editor at Scientific American who covers energy, environment and sustainability issues. Follow on Twitter @markfischetti.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Sisko 12:02 pm 12/13/2013

    Mark Fischetti shows the continued bias of the propaganda machine known as Scientific American when it comes to the topic of climate change.
    He writes- “Considering that climate deniers are constantly accusing IPCC scientists of not having airtight data, it took some guts for the experts to identify gaps in knowledge.”

    Mark- why don’t you stop being a hack of a writer? What exactly is a “denier”??? Anyone who does not agree with your system of beliefs or anyone who sees the actual data and sees that the IPCC’s conclusions are based on faulty models and highly unreliable. The many scientists who disagree with the IPCC’s conclusions ARE NOT looking for airtight data as you write. They are looking for conclusions to be based upon reasonably reliable data. The current set of models fail in that respect.

    Mark- you are an example of the writers that SA should eliminate if it wishes to be respected as a scientific journal and not a politically based propaganda machine.

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  2. 2. tuned 1:44 pm 12/13/2013

    Again we see the utterly false and greedmongering self centered responses of the fossil fuel lobbyists.

    Link to this
  3. 3. tuned 1:47 pm 12/13/2013

    The only long term reasonable and actionable answer is to be happy with less use of resources and less population explosion.
    Enlightened responsibility can defeat greed of all kinds.

    Link to this
  4. 4. Uncle.Al 2:22 pm 12/13/2013

    Multi-$trillion economic disruption worldwide (burn corn and algae; Go Green) plus the Carbon Tax on Everything are predicated upon “particular gaps in knowledge” like not knowing what clouds do.

    Social activism is feeding us to ourselves (less postage, handling, and user fees). Glory be ours by the years and the hours, and the days and the months and the gravestones.

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  5. 5. outsidethebox 4:15 pm 12/13/2013

    Why is the jet stream over Brownsville Texas rather than Winnipeg Manitoba? And has been for a couple of weeks this fall. Another question I wish they could answer.

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  6. 6. Prodigal Potter 4:58 am 12/14/2013

    The key problem with this piece is that it doesn’t recognise a truth it alludes to, namely that climatology isn’t a single science but a discipline based on multiple phenomena which are life-long pursuits for scientists in themselves. Geology, oceanography and local cosmology all play a part in climate behaviour, with their unknowns or assumptions only magnifying climatology’s uncertainties as suppositions become increasingly filled with uneducated speculation. To fully understand one scientific discipline in a lifetime is a huge achievement. To fully understand multiple disciplines is all but impossible.

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  7. 7. jayjacobus 10:06 am 12/14/2013

    Potter,

    Because of the complexities, forecasting is subject to the vagaries of the underlying causes. Few (no one?) would have predicted the temperature hiatus from 1942 to 1980. But few could predict the acceleration in warming in the next 86 years.

    Yet that’s been done and accepted by CO2 believers.

    In my opinion the forecast is questionable and should be replicated/refuted by independent statisticians.

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  8. 8. Rocket 8:12 pm 12/14/2013

    Here’s a NASA publication, from 2011:
    Hansen, J., Mki. Sato, P. Kharecha, and K. von Schuckmann, 2011: Earth’s energy imbalance and implications

    In it, James Hansen lists the earth’s energy imbalance at 0.58 watts/sq meter. He puts the cooling effect of aerosols at 1.6 w/sq m. So aerosols are extremely important. If human-caused aerosol pollution were to go to zero, global warming would rapidly accelerate.

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  9. 9. Postman1 9:39 pm 12/14/2013

    Rocket, having Hansen’s name attached lowers the reliability of the paper.

    Link to this
  10. 10. eco-steve 5:13 am 12/17/2013

    Heat absorbed by ice remains latent until it melts. Therefore, ice continues to absorb heat without temperature increasing, so the poles can warm considerably, but this can be dificult to detect.

    Link to this

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