Ask an Atmospheric Chemist

Is the earth's climate getting warmer?

Yes.  The 1990s were the warmest decade of any in the last 1000 years (www.ipcc.ch). 

The climate of the 20^th century shows two main periods of warming, one in the decades leading up to WWII, and the other in the years since the Rolling Stones released ‘Exile on Main Street’ in 1972.  The total increase in the global average surface temperature over the last 100 years is one degree Fahrenheit.  This global average value hides large regional variations.  For example the climate of Alaska has warmed by about 3 degrees F just since 1970 (http://climate.gi.alaska.edu/ClimTrends/30year/30yr.html).

Why is it getting warmer?

Mostly because of the greenhouse effect.  The greenhouse effect is straightforward.  In 1827 the French Mathematician Fourier (who gave us the Fourier Transform, and worked on calculating the trajectories of Napoleon’s cannonballs) wrote that the atmosphere acts as a greenhouse, since it is transparent to visible incoming sunlight, but prevents infrared heat energy from escaping.  Certain atmospheric gases absorb infrared heat (including water vapor, carbon dioxide, methane, laughing gas, ozone and the CFCs), while most all atmospheric gases are transparent to visible sunlight (nitrogen, oxygen and the aforementioned greenhouse gases).  The concentration of the greenhouse gases has been increasing since the agricultural and industrial revolutions, and the timing of their increasing atmospheric concentration matches the timing of the 20^th century warming very well.  The net effect of the increased greenhouse gas concentrations is roughly as if the sun has been turned up by 1 %, leading to the observed temperature rise. 

            The greenhouses gases are of course not the only factor affecting climate.  Volcanic eruptions change climate by filling the atmosphere with a cloud of particles, which cools the surface by reflecting incoming sunlight into space.  The largest eruption of the 20^th century was by Mt. Pinatubo in the Philippeans in 1991.  It cooled the planet by about a degree F for about a year.  Like volcanoes, industrial activity results in atmospheric particles (for example sulfate aerosol from coal) which are thought to have cooled the planet, resulting in the plateau in the temperature increase from WWII to the early 1970s.  A small amount of the temperature increase may be due to increased solar activity.

When will the truth of this become apparent?

When the doors of perception have been opened….

Some would link recent events like low water levels in the Great Lakes, and Midwestern and European flooding to climate change.  However, it is not possible to ‘prove’ climate change based on a single event.  Much stronger arguments can be made by averaging over large areas, and by examining temperature records extending back over a century.

Who is saying that the earth's climate is getting warmer and who is saying that this is not true?

Everyone agrees that the earth’s climate is getting warmer.  There are too many long-term temperature records (dating to the 1860s) for any serious person to claim otherwise.  Most of the disagreement concerns the cause of the warming—natural or due to human activity?  There is strong evidence that most of the warming observed over the last 50 years is due to human activities.  No one disputes that climate variations can also have natural causes—just think of the ice ages!

Where will the biggest effects be felt in the future?

It is projected that the oceans will rise by more than a foot by the end of this century, and that global (average surface) temperatures will rise by 4 to 8 degrees F.  The largest temperature changes will be seen away from the equator.  For example Minnesota and Alaska are projected to have temperature increases, on average, of 14 degrees F by 2100.  The biggest effects will most likely be felt in countries that do not have the resources to deal with the health and social problems created by sea level rise and drought (or flooding).

Can you provide some links or other resources about global warming?

The best place to start is the Intergovernmental Panel for Climate Change’s (IPCC) 20 page ‘Summary for Policymakers, available at:

http://www.ipcc.ch/pub/spm22-01.pdf

The IPCC website (www.ipcc.ch) is full of high quality free information, and is the source of a lot of the information I have written here.  Other sources include the Pew Center (http://www.pewclimate.org/) and the Canadian government’s website (http://www.climatechange.gc.ca/english/index.shtml).

What knowledge are most people missing about global warming?

I think the main point that mainstream media and public perception misses is that climate change is real, and that it’s already underway.  The 1990s were the warmest decade of any in the last 1000 years.  Another important point:  Most people are unaware that there has always been a strong natural greenhouse effect on earth, due to water vapor and carbon dioxide in the atmosphere.  This natural greenhouse effect warms the surface by about 60 degrees F, and prevents our planet from being a big iceball.  Human activity has simply changed the size of a preexisting effect.

Can you comment on the difference in world opinion vs American opinion about global warming?

Is there a unified American opinion?

 

It is always possible to speculate about the effects of talk radio, Reagan’s changes to the rules governing the ownership of media in America, and of corporate opinion on the American public discourse.  But that’s just an excuse.  Us Americans like cars, we like big houses, we like to own lots of stuff, lots of powerful electrical stuff.  The American lifestyle has consequences.  The question is, is our character strong enough that we are willing to take responsibility for the consequences of our actions?

 

As for the opinion of the rest of the world, well, virtually every other country, developed and underdeveloped, has ratified the Kyoto treaty to reduce greenhouse gas emissions.

Can you comment on America's share in causing global warming?

Table 1.  You know, you just can’t say enough nice things about those Canadians….

 

Americans use about twice the energy per capita as do the people of England, Germany or Japan (See World Bank table above).  Can we argue that we have twice the quality of life?  Of course not!  We don’t need to use so much energy in order to live well. 

In Sweden and Denmark, what do folks say about America's role in global warming?

It made headlines here when the Bush administration broke its campaign promise to take greenhouse gas emissions seriously.  Greenhouse gas emissions is one of a few key political issues separating the US and Europe right now.

Are scientists who question global warming ostracized or regarded with suspicion?

It is natural and healthy for all scientists to regard all other scientists with suspicion, and as far as ostracism goes, many would say that most scientist’s social skills were not all that good to begin with. 

 

I can give as an example a scientist at the Danish Space Research Institute, Dr. H. Svensmark, who is exploring the theory that modern climate change can be explained by solar variation.  His mechanism involves the modulation of cloud formation by ions generated by interstellar cosmic rays, whose abundance in the atmosphere is known to be affected by the solar wind.  Henrik has had to swim upstream at times, but that’s true of most scientists at his level.  On the last Friday of August, 2003, I was a guest at an all-day meeting at the Danish Space Research Institute organized in part by Svensmark.  Speakers were flown in from UCLA, Finland and Germany.  Everyone at the meeting seemed friendly enough to me, polite, I don’t remember detecting any ostracism.  (This could have been because DSRI neglected to publicize the meeting to their colleagues in the Geophysics department at the University of Copenhagen, who share the building, but we’ll let sleeping dogs lie.)  Henrik has been able to get funding for his research, and his papers have been published in well known peer-reviewed journals, even though many of us have a hard time seeing how his effect could do what he claims it can do.

How can we tell the difference between human induced climate change and change that would happen anyway?