Q&A: Global warming — a world of evidence
Editor's note: This Q&A occurred in October of 2005.
As one study after another has pointed to carbon dioxide and other man-made emissions as the most plausible explanation, the cautious community of science has embraced an idea initially dismissed as far-fetched.
The result is a convergence of opinion rarely seen in a profession where attacking each other's work is part of the process.
Every major scientific body to examine the evidence has come to the same conclusion: The planet is getting hotter; man is to blame; and it's going to get worse.
Climate researcher John M. Wallace of the University of Washington, UW research scientist Dr. Amy Snover and Ph.D. candidate in atmospheric sciences Justin Wettstein fielded your questions about global warming in a live Q&A session Tuesday. Thanks to everyone who participated.
I very much appreciated Sunday's article about global warming. A friend believes that this trend may in fact be good for us and our planet. Others argue that little can be done to slow the warming, and nothing significant would come of modifying our buying habits or creating green production requirements except to disrupt our economy. I believe that our society - nationally and worldwide - may break down, which could involve war as we compete for severely limited resources, including food and energy. But I don't have facts to respond to the statements of these friends. Would you describe some potential scenarios for how life could change and how I might respond to these people?
— Suzanne Krom, Seattle
And as for being able to "stop" global warming, your friends are right - that it's a hard challenge, but wrong to say that there's nothing we can do. If humans can cause the climate to change (and we can!) we can certainly stop doing so. See other posts for ideas about what to do and check out the Apollo Alliance (http://www.apolloalliance.org/), a "broad coalition within the labor, environmental, business, urban, and faith communities in support of good jobs and energy independence." The Apollo Alliance is pursuing a $300 billion, public-private program to create three million new, clean energy jobs to free America from foreign oil dependence in ten years.
What is the evidence that the global climate changes that are in question are the result of human behavior rather than a natural cycle? Hasn't the earth seen fluctuations in climate temperatures during periods where humans weren't burning fossil fuels?
— Doug Kilishek, Seattle
Some of the most dramatic climate change in the past was the alternation between glacial epochs, or ice ages, like the one that ended 15,000-20,000 years ago, and non-glacial conditions, like we're experiencing now.
The cause of these swings was the subtle variations in the Earth's orbit around the sun due to the pull of the other planets. These orbital changes don't change the total incoming solar energy significantly, but they dramatically change the strength of the sunlight over high northern latitudes, like Northern Canada, during the summer season.
The conditions that favor weak summer radiation in these areas are:
1. A large tilt to the Earth's axis
2. A large departure of the Earth's orbit from a circular shape, so that the Earth is much closer to the sun in part of its orbit than in the other part.
3. The Earth is farthest from the sun during the Northern Hemisphere's summer.
When these three things occur, solar radiation is weak in the high northern latitudes in the summer. Under these conditions, snow and ice that accumulate during the winter don't melt during the summer, so the ice builds up and an ice age results.
The end of the ice age comes when the orbit arranges itself so that solar radiation during summer is very strong. These changes take place very slowly - over thousands of years. In contrast, greenhouse warming is taking place much more rapdily - on a time scale of a century.
Hence ecosystems have much less time to adjust to the changes.
Human civilizations have experienced climate change before, but nothing as dramatic worldwide as we're seeing now.
Why are we convinced the current warming is not due to natural processes, like these orbital changes? First: Because we know greenhouse gases are accumlating in the atmosphere in levels that haven't been experienced in the past few tens of millions of years.
Second: Because the pattern of the observed warming fits the pattern we would expect from warming caused by the buildup of greenhouse gases. (ie- almost all areas of the planet are warming; the Earth's surface and lower atmosphere are warming; the upper atmosphere is cooling; the temperature changes are greatest in the Arctic during winter.)
Third: The warming is much more rapid than most of the natural variations we've seen in the past.
Paint a picture of what the landscape and lifestyle of the Northwest will look like in 10-20-30 years under the current global warming conditions.
— Tim Cummins, Black Diamond
As a result, the PNW is likely to see:
Changes in water resources:
• Decreased mountain snowpack
• Earlier snowmelt
• Higher winter streamflow in rivers that depend on snowmelt
• Lower summer streamflow in rivers that depend on snowmelt (most rivers in the PNW)
• Earlier peak (spring) streamflow in rivers that depend on snowmelt (most rivers in the PNW)
• Decreased water for irrigation, fish, and summertime hydropower production
• Increased conflict over water
• Increased urban demand for water
Changes in salmon:
• Increased difficulties due to increased winter floods, decreased summer streamflow, and increased water temperature
Changes in forests:
• Seedling regeneration increased in high snow forests, decreased in dry forests
• Increased in high snow forests
• Decreased in dry (east-side) forests
• Potential increases in forest fires
• Potential for extinction of local populations and loss of biological diversity if environmental shifts outpace species migration rates and interact negatively with population dynamics.
Changes along the coasts:
• Increased coastal erosion and beach loss due to rising sea levels
• Permanent inundation, especially in south Puget Sound around Olympia
• Increased coastal flooding due to sea level rise and increased winter streamflow from interior and coastal watersheds
For more information about these and other impacts of climate change, see http://www.cses.washington.edu/cig. You might also be interested in a report coming out next week from the Puget Sound Action Team summarizing climate impacts on the Puget Sound marine ecosystem and in a conference being held by King County later this month on climate impacts on Washington state (http://dnr.metrokc.gov/dnrp/climate-change/conference-2005.htm)
What is the relationship between population rise in Third World countries and global warming? What about the rumor that HIV-AIDS and other diseases are man-made to reduce population and then to stop global warming?
— Zela, Atlanta
As to your question on creating disease to eliminate population, obviously that's morally bankrupt.
I heard a while ago that warming was 2 degrees Celsius, with a +/- of 2 degrees worldwide. Has that changed to a point where there is statistical significance?
— Mat Chavez, Seattle
Note that essentially no climate models show cooling and also that the temperature scale used in the IPCC reports is in Celsius, so multiply by 1.8 to get change in degrees Fahrenheit.
This is really out there, but millions of people smoke cigarettes and it all adds up. How much does smoking contribute to global warming?
— Linda Neilsen, Kent
Isn't it true that scientists in the 1970s said the earth was cooling?
— (several readers)
Most of us were very skeptical of these claims and largely ignored them. Within a few years, the pendulum had swung the other way and scientists were beginning to recognize that the worldwide climate had actually been warming quite dramatically since the early 1970s.
The cooling scare involved a handful of scientists and lasted only a few years, until evidence proved it wrong. In contrast, nearly the entire scientific community is concerned about global warming and this concern has been steadily getting stronger as the evidence accumulates.
When we moved here in 1950s I noted to my mother the snow capped mountains to the west of our home. The view was of the mountain tops only. My mother answered that what she saw were only white clouds. Today, from the same viewpoint, she would not see white clouds but mountains. Has anyone documented the decreasing snow and glaciers of the Olympic Mountains in Washington state on film over the past years?
— Linda Neilsen, Kent
When crude oil is removed from the ground is it replaced with any type of filler?
— Linda Neilsen, Kent
What are references for world temperatures and sea levels over the past 75,000 years. Can you recommmend good books?
— Bob Moyer, Bellevue
What is the major argument used by the "debunkers" of global warming? What can be done by the average citizen to help stop global warming?
— Kate Yamamoto, Bellingham
In an earlier post [below] I described some things that an "ordinary" person (is there any such thing?) can do about global warming. These could be broken down as follows:
• Individual action (reduce actions that rely on fossil fuels, e.g., in transportation, home heating and lighting, consumption.)
• Collective action (encourage friends and neighbors to do the same, elect politicians who will make the needed policy changes, work for broad institutional change.)
Shifting the world's economy away from its dependence on fossil fuels is a huge challenge that won't be accomplished by any one change. It will require actions big and small by individuals, corporations and governments around the world. Sometimes people feel like nothing they do matters, but I like to say that the only thing that matters is what people do.
Is there any credence to the concept that tropospheric warming may be partly due to oceanic warming and not the reverse? For instance is atmospheric reradiation in the IR (infrared) deeply penetrating or as deeply penetrating as UVB (ultraviolet)?
— N. Finley
What if just more human beings are causing global warming? I remember going to a cold unheated dance hall and by the time all the people arrived the temperature was nice and warm. Also, my computer room is 5 degrees warmer then my living room, approximately the same square footage.
— Gloria Anderson, Lynnwood
Brazil by law requires the manufacture and use of biofuels, and cars built to burn these fuels are common, since 1979. GM actually builds these cars in Brazil. Why does the U.S., the largest consumer of fossil fuels, still refuse to change? This will not solve all our problems, but its a large step in the right direction.
— Al, Seattle
Why are the concerned scientists obsessing on carbon dioxide and ignoring other aspects of the problem? The upward trend on the hockey stick curve starts also at about the time of the introduction of steam and internal combustion engines. While these do emit carbon dioxide, they also dump billions of BTUs of waste thermal energy into the atmosphere and the oceans. Why not some support for finding non-entropic heat engines? In an isentropic expansion half of the "expended" thermal energy produces mechanical energy and the other half expands the working fluid and is then dumped either directly into the atmosphere or through a condenser. Work obtained through an isentropic compression would not involve ending the process with an expanded fluid. I have been trying to tell people this for over thirty years but no one will listen.
— Patrick McNenny
Is global warming reversible?
— Tammy, Seattle
So, just what can an ordinary person do to help stop this problem?
— Marla, Seattle
What about the possibility that the migration of people from the continental heartlands to the coastlines contributes to global warming as the balance between coastline and inland heat is thrown off and in some unknown way increases ocean warming? I do understand that warming is the same in both urban and non-urban areas. Specifically, as populations have moved to the coastlines dramatically in recent years, could this shift in the location of the populations affect global warming? Pollution has long been with us but what is different today than just a few years ago is where the populations around the world are congregating, namely at the coasts. Urban and rural warming and the location of that warming are not the same. Thank you.
— Linda Neilsen, Kent
Why does The Times ignore the fact that Greenland, Iceland and the Antarctic Continent are cooling? The land-based glacial ice in these 3 areas constitute 96 percent of the total land-based ice on the planet. Why does the Times insist that "consensus" automatically means "truth"? In science, those who refer to "consensus" usually have a hidden agenda. Since there is no technology that exists today to reduce the amount of atmospheric aerosols, what do you propose we do about it?
— J. R. Leicester, P.E., Shoreline
Greenland, Iceland and Antarctica have cooled very slightly over the past few decades, in contrast to most areas of the Earth, which have experienced warming. Temperature trends over the Earth's surface are not uniform because, in addition to the warming, there have also been changes in circulation patterns, like El Nino and the Arctic Oscillation and the Pacific Decadal Oscillation. Changes in these patterns accelerate the warming in some areas and retard it in others.
Two areas where the warming has been accelerated are Siberia and the Antarctic Peninsula, which extends from the Antarctic continent toward South America. The Antarctic Peninsula is the place where warming is causing the collapse of some of the ice shelves.
I live where the weather is cold, wet and dreary. Might global warming actually benefit us by bringing warmer, sunnier, and drier days?
— Kurtis Jones, Seattle
Are any scientists looking at ways to absorb carbon dioxide from the air as an alternative to reducing carbon dioxide emissions from human activity?
— Don Schaechtel, Seattle
Personally I favor reducing our dependence on fossil fuels not only to slow the rate of greenhouse warming, but also to preserve what's left of the world's precious petroleum reserves for our grandchildren and their grandchildren and to limit the environmentally destructive mining of coal.
I learned that water expands (fills up more space) when it freezes. Conversely, doesn't water contract when it melts? Aren't scientists forgetting this when they preach impending doom about the coming Waterworld?
— J. Adam Pang, Ellensburg
What are some ways an average person can decrease their contribution to global warming?
— Andrea Liggett, Redmond
Recent imaging from the Mars Global Surveyor shows a rapid depletion of glaciers and ice fields on the Martian surface. Analysis of this data shows this to have taken place over the last several hundred years. (Aviation Week and Space Technology Oct. 3, 2005) What is the likelihood of a common cause for the warming of the Earth and Mars?
— Pat, Federal Way
I understand that grapes were growing in parts Norway during the Medieval Warm Period where it is currently too cold to grow grapes today. If it is warmer today than in the past why is it currently too cold to grow grapes in those same areas of Norway?
— Janice Mehringer
I have been under the impression that the MIT Global Change Joint Program is the primary organization gathering and disseminating information on weather change. http://web.mit.edu/globalchange/www/. Yet, I rarely see it mentioned as an information source by those scientists forecasting a disastrous future-world due to human enabled weather change. Is it a primary information source for serious scientists? Is there a split between the MIT group and others studying global warming? What's your opinion of the scientists who run that program?
— Steve Ginn, Kirkland
Why does the Law Dome Antarctica Ice Core show that atmospheric CO2 began a significant increase around 1750, a century before significant fossil fuel burning began during the Industrial Revolution?
— Ken Schlichte, Tumwater
I'm curious if you share the view of reporter Sandi Doughton inherent in her Times article, "The truth about global warming," that scientific fact is determined by majority vote? It seems to be the only consistent criterion considered.
— Doug Parris, Shoreline
How can scientists be sure that the warming that has occurred during this century isn't a "normal" occurrence, especially since the last ice age ended only 12,000 years ago? How do they know that such a warming did not occur 5,000 years ago or 100,000 years ago? Or a million years ago?
— Robin Heflin, Camano Island
In what ways has global warming affected the Pacific Northwest?
— Josh, Lynnwood
I am compiling research on global warming for a geography project and was wondering if you thought that global warming was the main catalyst behind Katrina? Do you think this may have dramatically changed people's views about signing the Kyoto Protocol?
— Deborah Sneddon, Glasgow, United Kingdom
I heat with wood. I once read that the same gases are given off, be it high temperature oxidation (in my high efficiency wood stove) or slow oxidation (rotting out in my woods). True statement or not?
— Dennis Coons, Snohomish
The natural environment changes over time. There have been ice ages and warmings. Why would 50 years of activity make any difference to me? Isn't the global warming argument mainly created as a vehicle to forward radical environmental laws?
— Dale Smith, Sammamish
Has there been a study on the effects of the reduction in "green" — trees/plants — in relationship to increase in carbon dioxide? What correlation is there between this reduction in green and global warming - i.e. less green increases global warming?
— Alan, Seattle
We have heard the negative arguments as to global warming. Now, in reading the N.Y. Times this morning a series of articles advocating some of the positive points of global warming are coming forth. I am well aware of the negative points and agree with them. However, what are the positive points and how will areas as Seattle, Boston, N.Y., etc. deal with rising oceans?
— Ed Jenkins, Seattle
Barring a precipitous disintegration of the continental ice sheets, the buildup of sea-level will be so gradual that cities like Seattle and New York will be able to adjust without a great deal of hardship. It's the low lying coastlines like those in Louisiana and Bangladesh and on coral atolls that will bear the brunt of the damage.
If, by some miracle, every CO2-producing machine in the world (not including biological) were to suddenly stop working, how long would it theoretically take to reduce the rate of change in global warming?
— Liora Van Natta, Seattle
Mike, since infrared greenhouse radiation cannot penetrate into the oceans (beyond a "skin" of thickness 10 microns)**, just how does the greenhouse effect warm the ocean?
(**from physical optics theory and actual measurements)
— Fred Singer, Arlington, Va
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