We are days before the official beginning of winter and much of the nation is gripped in cold and snow, so it might seem an odd time to discuss global warming.
Here is the science, and a few personal comments from a seasoned meteorologist.
While this topic has stirred up controversy and some strong reactions, it truly is pretty simple science - when you add heat to something, it gets warmer!
I address this topic at some peril! In many ways, the job description for the TV "Weathercaster" is to simply be the nice, friendly person that tells you what the high will be, how much snow will fall and what to expect next weekend.
I have found that, especially in recent years, the topic of global warming can stir up deep emotions within viewers and can bring some rather rough responses via e-mail and Facebook.
Nonetheless, the TV meteorologist is often asked to provide their viewers with insight and explanations on earthquakes, meteors and comets, tsunamis and volcanoes. For many Americans, we are as close to a scientist as they will get, and they invite us into their living rooms.
I hope that, even if you do not agree with my comments and explanations, you will appreciate the attempt and still choose to watch my weather reports.
So, with that said, here we go!
Climate. Has. Always. Changed.
It is absolutely true that the Earth's climate has cycled through great changes over the course of our geologic history. These changes are obvious in the fossil record - Denver was once under a great shallow ocean!
These changes are due to a variety of causes, from shifts in the Earth's orbit on its journey around the Sun, to changes in the output of energy from the Sun to changes in atmospheric chemistry.
One of the key components to our Ice Ages has been what are called the Milankovitch Cycles. These long term changes in the shape of our orbit and the shift in the tilt of the Earth work like the complex gears of a clock, gradually switching our planet from Ice Age to warmer periods and back again.
The Milankovitch Cycles are well documented and have been a primary driver of our changing climate for hundreds of thousands to millions of years. Here is a link to learn more.
The Greenhouse Effect is not new science.
If not for this effect, the Earth would be about 60 degrees Fahrenheit colder -- a lifeless ice planet.
In 1825, a French mathematician named Joseph Fourier calculated that given the distance from the Sun, the Earth should be much colder. He theorized that it was the atmosphere that trapped enough heat from the Sun to make our planet habitable.
In 1865, John Tyndall, an Irish physicist - did early experiments with carbon dioxide and discovered that CO2 was very effective at trapping long-wave or Earth energy.
In 1895, a Swedish researcher named Svante Arrhenius theorized that a doubling of carbon dioxide in the atmosphere would cause the Earth's average temperature to increase by several degrees.
In the past 200 years (since the Industrial Revolution) the increased burning of fossil fuels has released vast amounts of carbon dioxide into the atmosphere. The concentration of CO2 has risen in the past two centuries from 280 parts per million (ppm) to just over 400 parts per million.
I am often asked about how such a trace gas can be so important. Consider that 400 ppm of Carbon Monoxide would render us unconscious and close to death. Unlike CO2, CO is a poisonous gas, but it illustrates the fact that small amounts do matter. Carbon Dioxide is not deadly, but it is highly effective at retaining terrestrial energy in our atmosphere.
Think of each molecule of carbon dioxide like a feather in a down comforter. If there are not very many feathers, your body's heat will escape through the comforter and you will be cold. If you keep adding feather after feather, the comforter becomes much more efficient at holding in your body heat and you stay warmer.
Our atmosphere can be thought of as a giant comforter and modern scientists have calculated that a doubling of the CO2 from pre-industrial levels will result in a net increase of 4 watts per square meter of stored energy over the entire surface of the Earth. That is about a night-light’s worth of heat over a square meter, but taken over the vast surface area of the Earth, this is a tremendous amount of energy!
The heat retaining characteristics of carbon dioxide can be measured in a lab and can be further verified by studying the changes in CO2 concentration and global temperature from Ice Age to Ice Age (tree rings and ice core data). The data shows that climate warms or cools about 3/4 of a degree C per W/m2 of forcing.
Since each doubling of CO2 adds about 4 W/m2 of forcing, and without strong policy to switch the world to non-carbon energy, we are on track for two doublings. So “business as usual” would add 8 W/m2 of forcing by 2100.
At the end of the last Ice Age, the melting ice sheets dropped the albedo (reflectivity) and the oceans released CO2 and methane. The total climate forcing was about 6.5 W/m2, and the Earth warmed about 5 C over 10,000 years. Notice this is also about 3/4 of a degree per Watt. If China, India, and Africa industrialize with coal, we will add more than that in 100 years. Wow!
Methane is an even more powerful "Greenhouse Gas" and is being released as permafrost melts in the high latitudes and from leaking at natural gas well sites - fortunately this leaking is something we can fix and contain, if we choose.
What about Water Vapor?
Water vapor is a greenhouse gas, like carbon dioxide and methane. Water vapor and clouds account for 65 to 85 percent of the greenhouse effect, compared to a range of 10 to 25 percent for CO2. So why all the attention on carbon dioxide?
The answer is that water vapor is responsible for a major portion of Earth’s warming over the past century and for projected future warming. However, water vapor is not the initial cause of this warming.
The increase in carbon dioxide, although small compared to the volume of the atmosphere is very important – an increase in water vapor in the atmosphere is a result of this warming.
In general, the amount of water vapor in the troposphere does not vary significantly over time so long as temperatures remain stable. However, if some external forcing causes tropospheric temperatures to increase, there will be a water vapor feedback.
Warmer air can “hold” more humidity than cooler air. Additional water vapor concentrations (resulting from higher average temperatures) will trap even more heat and result in additional warming.
Increasing temperatures also influence cloud formation, which both trap heat below them, heating the Earth, and increase the reflectivity of the Earth (the albedo) by reflecting light off their white surfaces, cooling the Earth.
There remains uncertainty regarding the magnitude of cloud feedbacks, though many researchers believe that the effect is neutral or slightly positive.
Weather is NOT Climate!
It is very important to realize that a heat-wave, tornado outbreak, record flood or major blizzard is not climate -- it is weather! The weather goes through tremendous fluctuations from day to day and even hour to hour -- let alone over the course of weeks, months or even years.
An analogy that I like to use is “weather is one play in a football game, climate is the history of the NFL!
When people joke to me that “you cannot even predict the next few days with certainty, how can you predict 100 years from now?” I certainly agree that weather forecasting is not always as accurate as desired, but in many ways weather is much harder to predict than climate.
For example, if you wanted to get away from the cold in January, would you head to Miami or stay in Denver? The climate of Miami would dictate that you buy an airline ticket and head to the beach.
The weather of Miami could mess up your plans if a strong cold front hit Florida during your trip. In fact, Miami might be 45 degrees and windy, while Denver basks in 65 degree weather due to a Chinook!
As the climate warms, the higher average temperatures in the western United States will likely be manifest in more drought and wild-fire concerns in the decades to come. Because we are far away from large bodies of water, higher temperatures here are not usually associated with increased humidity - in fact, just the opposite.
Drought is not just a lack of precipitation, it is also related to the amount of evaporation of moisture from the soil. Even with the same amount of annual precipitation, higher temperatures would result in more frequent drought.
El Nino and other ocean circulations
El Nino and La Nina episodes may altered in the coming century. The periodic warming and cooling of the Pacific Ocean along the Equator has enormous implications on global weather.
These warming and cooling events in the ocean need to be taken into consideration over the long term, not used as singular examples of a change in the climate.
However, as the overall temperature of the Earth increases, it is quite possible that we will see stronger versions of both El Nino and La Nina. The result will be increasingly severe individual episodes of heat and drought, storms and floods.
There are several other periodic ocean circulations that are not as "famous" as El Nino or La Nina. These circulations help to store vast amounts of the heat in the ocean water. The periodic release of the stored heat from the ocean to the atmosphere is a key reason that we see the warming occur in steps instead of a gradual ramping from year to year.
Back in the 70s, they said it was COOLING!
I studied meteorology at the University of Wisconsin at Madison in the 1970s. At that time, Dr. Reid Bryson, one of the founders of the UW Meteorology Department was lecturing about the prospect of a "New Ice Age". The cause, Bryson theorized, was due to the increase in tiny particles of smoke and dust during the Industrial Revolution.
In fact, even at the time, most researchers, including Bryson, felt that the increase in CO2 would eventually offset this "dirty window" effect and the climate would begin to warm.
This is an important point, as many anthropogenic global warming (AGW) skeptics still bring up the "1970s Global Cooling Theory" as an argument that the current consensus among climate scientists has been an "about face" form the 1970s.
Here is an article about this from the Bulletin of the American Meteorological Society.
The Climate Petition, Climate-gate and other skeptical reports
I am sometimes asked about the “30,000 scientists that signed a petition”.
The petition that has been in circulation since 1998 claims to bear the name of more than 30,000 signatures from scientists who reject the concept of anthropogenic global warming.
The petition suggests that thousands of scientists have rejected the concept of climate change, and was developed be a self-described research group by the name of the “Oregon Institute of Science and Medicine”.
The group solicited signatures for a petition (known now as the Oregon Petition) to have the United States reject the Kyoto Protocol to set internationally binding emission reduction targets.
Signatories are approved for inclusion in the Petition Project list if they have obtained formal educational degrees at the level of Bachelor of Science or higher in appropriate scientific fields.
It is misleading for the signatories to be considered climate scientists or even top researchers in their field. In fact, based on the group's own numbers, only 12 percent of the signers have degrees (of any kind) in earth, environmental, or atmospheric science.
Careful study of the list revealed the names of fictional characters from the “Star Wars” movies as well as the name of pop singer Geri Halliwell from the “Spice Girls” band. Critics of the petition had added bogus names to illustrate the lack of accountability the petition involved, including the difficulty—the practical impossibility—of verifying even the actual existence of each of the signatories, not to mention their expertise. To make the latter point, someone had added the title of “Dr.” to Halliwell’s name.
The Heartland Institute and other groups frequently post essays that are skeptical of the impact of increasing carbon dioxide on the Earth’s climate. Although a variety of views is often helpful to further scientific understanding and spur new research and ideas, many of these groups have ties to donors that are very politically active.
A fairly quick search of these groups is available here.
The release of private e-mails from the University of East Anglia in late 2009 raised some questions about a hidden agenda among the leading climate scientists around the world.
The timing of the release of the e-mails came just before the International Climate Conference in Copenhagen and did divert the focus of the agenda of that conference.
There were about 60 megabytes worth of e-mail exchanges released, but only a small fraction of the private comments truly raised any concern. Scientists often speak casually among themselves in a short-hand of sorts.
In this respect, saying something such as "the trick in this problem" does necessarily mean an actually "trick" or sleight of hand, but rather a method of calculating something.
Granted, it does not sound good when clipped out of context, but there were no comments such as "boy are we pulling a fast one on the world, we are going to get rich!" Another comment that was brought up is, "we cannot show any warming, and it is a travesty that we cannot". In this case, the comment refers to a lack of an adequate monitoring system to show the warming in the deeper waters of the ocean.
The warming is there, we just do not have the instruments covering enough of the ocean to measure it adequately. Once again, it looks bad when taken out of context, but actually had a very different meaning.
The Arctic Ice
Satellite measurements since the late 1970s have shown that the sea ice has dramatically diminished. Sea ice does grow and shrink due to natural cycles, but it appears that the current state of the ice is near historic lows.
The sea ice is highly reflective, dark open ocean is just the opposite. As more of the Arctic remains open, the waters will warm and this may play a significant role in altering the phases and intensity of many ocean circulations.
My Personal Thoughts
I am not a climate scientist; my expertise lies in a much, much shorter time-frame. However, I spend a great deal of time on-line and at seminars with many of the best climate scientists from NCAR and other research institutes from around the world.
My opinion is that we are having a significant impact on the warming of our climate, and this will make weather events more extreme. With a greater amount of energy in the climate system, there will be drier droughts, heavier rains (although more spotty), bigger winter storms and more powerful severe weather events.
The physical science is pretty straightforward, the political science, if you will, is the very hard part.
It is correct that the United States cannot solve the problems we face alone. However, we can lead in the development of the new technologies needed to produce the energy we need, protect and preserve our valuable water supplies, reduce the amount carbon dioxide being added to the atmosphere and deal with the consequences of rising sea levels. It takes political will and scientific advances - but first, it will take realizing the enormity of the problem.
In the words of Albert Einstein, "the problems we face cannot be solved with the same level of thinking as when they were created".
Our Very Special Planet
When the Soviet Cosmonaut Yuri Gagarin, the first human in outer space, reached the top of our atmosphere and gazed out of his small porthole, he was terrified. He was not worried about his spacecraft, he was shocked by how thin and fragile our atmosphere appeared against the cold blackness of space.
Gagarin later explained that he had always been taught that we lived at the bottom of a "great ocean" of air. From his tiny spacecraft, the ocean looked more like a shallow puddle.
As far as we know, out of the vastness of the universe, the planet Earth is the only place that harbors life. Someday we may find other worlds that provide an environment gentle enough to enable life to form, but for now, this is it, our lonely outpost in the corner of a galaxy.
It seems prudent, patriotic and reverent that we do what we can to conserve and protect the fragile envelope of air that allows us to live on planet Earth. The legacy we leave future generations depends upon the actions we take in the coming years. Our heirs will be the judges of our success.
In the words of Thomas Jefferson in 1789, "I say the Earth belongs to each generation during its course, fully and in its own right, and no generation can contract debts greater than may be paid during the course of its own existence."