In cooperation with PlanetThoughts.org, I have conducted this interview between myself and a composite, typical Anthropogenic Global Warming skeptic. That is to say, these are my answers to the questions and doubts typically posed (in many online discussions as well as at open meetings) by those who doubt that humans are causing the planet to become significantly warmer. We felt that this interview format of presentation would be more engaging, and more clear, than simply expounding a series of facts in a vacuum.
Skeptic: When it comes to determining whether there is an increase of temperatures on the planet, and how big the increase may be, how accurate are these temperature measurements? I have heard that scientists have, for some reason, chosen to measure in some areas that happen to currently have temperature increases, while ignoring other areas that currently have temperature decreases.
JH: Let's start with accuracy. The accuracy of modern thermometers is better than 1 degree Celsius, in some cases much better. One might ask how we can distinguish trends that might be less than 1 degree Celsius with these instruments, which is an excellent question. Instrument errors can be divided into random errors (noise), systematic errors (biases), and personal errors (incorrect measurement technique). Random errors are reduced by taking many measurements over time, and the magnitude of the error decreases with the square root of the number of measurements. For example, two measurements have an error which is only about 70% that of a single measurement.
For most stations, we have thousands of measurements. Furthermore, by fitting a curve to a series of measurements and taking a moving average of the data, we can bring the errors down considerably.
Systematic errors are known patterns of error, such as a thermometer always reading 15% high. One systematic source of error in the temperature record is called the urban heat island, which is the result of cities spreading out over areas where thermometers have been placed (for example, at an airport after which the city grows around the airport). Systematic errors can usually be estimated and compensated for. For example, if we have a thermometer placed away from the city and another in the city we can find a relationship between the area of the city and the temperature error, and this relationship can be used to correct the city measurements.
Another example of a systematic error has to do with where we get our measurements from. The bulk of measurements come from the Northern Hemisphere, and particularly Europe and North America - these are the areas where temperature measurement was first developed and systematic observations began. Other continents are increasingly well instrumented, however, as organizations such as the World Meteorological Organization, an arm of the UN, work to get stations established in Africa, Asia, and South America. That said, there have been some thermometer measurements in all of these continents for a long time, and those data are vital for obtaining a correction.
The oceans present a bigger challenge, since many ocean areas have no fixed platform from which to make measurements. Some stations exist on islands, and many ships take measurements as well, and these observations are all recorded and archived at multiple locations. Just as with the urban heat island, a correction can be obtained to compensate for the reduced number of measurements in certain areas.
When all of the corrections are applied to the series of measurements over space and time, and multiple measurements are combined to reduce error, we get a global temperature time history over the past 100-150 years with an accuracy of about one tenth of a degree Celsius, which is definitely good enough to reveal trends in temperature.
I would add here that the gaps in the observation record (especially for oceans and less populated areas) are a major focus of effort in the scientific community, and are discussed often at scientific meetings.
The limiting factor in these measurements isn't that scientists don't want the data - oh, how we wish we had it - but funding... The places from which we have the fewest measurements are exactly those where it is most expensive to put instruments. I would urge anyone who is concerned about the coverage of measurements to put pressure on their political leaders to provide funds to establish and maintain stations in as many places as possible.
Skeptic: I have heard that although ice is melting in the Arctic area, it is increasing in the center of Greenland, and in the Antarctic. Doesn't this cancel out? Why don't global warming advocates ever mention these facts?
JH: Sea ice (this is, frozen seawater) is melting extremely rapidly in the Arctic. The area covered by sea ice has decreased about 40% since the 1950s, and is currently disappearing at the rate of about 7% per decade. The year 2007 was another record low year for sea ice cover, and we can expect this trend to continue.
Land ice begins as snowfall, which piles up and compresses under its own weight to form glaciers and ice sheets such as the ones in Greenland and Antarctica. The amount of snowfall in the centers of the Greenland and Antarctic ice sheets is indeed increasing, which is exactly what we would expect. Warmer air holds more water vapor, and a warmer atmosphere will lead to a more active cycling of water, meaning more precipitation in many places around the world.
Unfortunately, the additional precipitation in the centers of the ice sheets isn't enough to make up for the loss of ice by melting and calving (breaking off of icebergs) around the edges. Greenland's mass balance (the difference between snow accumulation and losses my melting and calving) is negative and growing more so, and the region where melt is taking place is spreading further into the interior of the ice sheet. In fact, the extra snowfall higher up in the ice sheet may be acting to increase the flow rate of ice out to the edges where it melts.
The mass balance of Antarctica is not as clear, some measurements show a slight growth while others a slight loss. The volume of ice on Antarctica is about 10 times as much as Greenland, however, and we would expect it to take much longer to react to overall warming of the atmosphere. That said, there have been some extreme mass loss events recently such as the breakup of the Larsen ice shelf.
Skeptic: Earth may be getting warmer, but so is Mars. This is strong evidence that warming we are experiencing is a normal process related to cyclical sun activity and earth positioning, with minimal input from human activities. Why should we call this warming a human-caused phenomenon?
JH: Climate change is not an either-or situation. There are many natural cycles of climate driven by changes in the Sun and in planetary orbits.
The Sun is known to have 11-year and 22-year cycles, and quite likely cycles of hundreds and thousands of years as well. The climate changes on Mars are extremely interesting and understanding those will help us greatly in discriminating between human-caused and natural climate variability, as well as calibrating our models of how atmospheres respond to external influences.
Could solar cycles of hundreds of years influence our climate? Absolutely, and there is some evidence of this in what is called the "Maunder minimum" and the Little Ice Age period that lasted from the 1300s to the 1800s. This is a very active area of research in climatology, and I have seen many presentations on this at conferences. The warming over the past 150 years, however, is of greater magnitude and is happening faster than can be explained by solar cycles or orbital variations (such as those that are responsible for the periodic ice ages the Earth experiences).
Skeptic: Although Hurricane Katrina was catastrophic, and there was a record number of hurricanes in the 2005 season, we have had two subsequent years with just normal or below-normal hurricane activity. If the oceans including the Atlantic Ocean and the Gulf of Mexico are warmer, and that warmth caused Katrina and the other hurricanes of that one active year of hurricanes, why has that not happened each year since 2005?
JH: Any climatologist that would assert that Hurricane Katrina was stronger because of global warming would be irresponsible. There are cycles such as El Nino/La Nina that can affect the number and strength of hurricanes on time scales of 3-5 years, while the greenhouse-driven global warming is on substantially longer time scales.
There is some evidence that warmer ocean water will enhance tropical cyclone activity, but in my opinion not conclusive enough to make any solid statements about a particular storm or even a year or two of strong hurricanes. This also is an extremely active area of research.
I would add that while we wait for more results on hurricanes and global warming, there are many things we CAN do to reduce loss of life and property from these storms. For example, improving warning systems, systems to protect cities from storm surges, reducing the population and development in threatened coastal areas, and putting in place disaster management systems (which failed so miserably in the aftermath of Katrina).
Skeptic: The cause-and-effect relationship between CO2 and temperature is not proven. There is some evidence, for example, that increasing temperatures may CAUSE an increase in CO2, not the other way around. So, again, why blame human beings and CO2 as being a cause for
heating up the planet? Isn't this just liberal self-hatred?
There is a clear and undeniable relationship between CO2 and temperature. Without the greenhouse effect, the Earth's surface would be about 30 degrees Celsius colder than it is. One can show in a laboratory quite easily the way that CO2 absorbs infrared radiation and warms an atmosphere. During the Cretaceous period (when dinosaurs walked the Earth) the atmosphere had several times as much CO2 as today and was much warmer.
That said, CO2 plays a complex role. There are feedbacks in the Earth's climate system that work exactly as you describe. For example, higher temperatures can cause the release of methane from land surfaces once frozen, in turn increasing the amount of greenhouse warming due to carbon in the atmosphere. Ice core evidence does show CO2 and temperature moving together, with temperature having a slight lead over CO2 at some times and slight lag behind CO2 other times.
One might say that this is a chicken-and-egg problem, but either way we end up in a skillet... It's clear that no matter which one leads or lags, having more CO2 in the atmosphere certainly can't make matters any better.
Skeptic: If temperature increases a few degrees, how big a difference can it make? Plants and animals will adapt, and those in colder climates will benefit by longer growing seasons and less need for fossil fuels.
JH: The Earth has indeed gone through many climate changes of much greater magnitude than even the worst case global warming predictions suggest, and life managed to survive, including humans. We did make it through several ice ages, after all! Will plants and animals adapt? Not much at all. The speed of the changes is simply too fast for evolution to change species. Instead, species adapted to climates will not be able to survive and will be replaced by other species that move from other places. This will be particularly true in the Arctic, where entire habitats will be gone.
Remember, too, that the warming is adding to other sources of habitat loss including deforestation, segmentation, and pollution. The rate of species loss today is roughly as great as it was 65 million years ago when the dinosaurs and about 60% of all other species became extinct. Some changes are simply too rapid for adaptation. People may have different moral views, but I feel that the loss of species, where that loss is caused by wasteful human behavior, is a crime of negligence. Knowing that we could prevent that loss and deliberately not making those choices makes it a crime akin to genocide.
Extinction is forever...
Some plants and animals will do much better in the changed climates, particularly those that reproduce quickly and are able to live in many different environments. Unfortunately, those organisms are what we call pests. We can expect the northward movement of insect and bacterial parasites into areas where they have been rare. The fire ant expansion into Texas and northward is just one example. Invasive species of all kinds will present a major problem to agriculture and public health.
Some people will do better also, while others suffer. Some people living in the Arctic, namely those with a Western culture, will manage quite well with the warmer climate and longer growing season. The indigenous peoples, however, will find their natural environment changing continuously and traditional food sources increasingly difficult to obtain - making them increasingly dependent on government assistance as there are few jobs. The Arctic will be opened up to transportation, agriculture, and industry as never before in our history, which will also impact the native cultures but benefit immigrants from the south.
People living in coastal areas (numbering in the hundreds of millions worldwide) will not benefit; the contrary is true. Even a slight rise in sea level (and the expectation is about half a meter rise in ocean level rise by the end of this century, with typical range estimates of between one-quarter and one meter) increases risks from storm surges, meaning that these people will have to be relocated. Increased temperatures will cause increased evaporation in continental interiors, making non irrigated agriculture more challenging even as other areas benefit from more precipitation.
Will global warming destroy civilization? Certainly not, humans are inventive and adaptable. But adapting to the future world will be very, very expensive at a time when populations are increasing and resources more scarce. The suffering will fall on those least able to adapt, and the cost in human life will be great. A study commissioned by the US Department of Defense indicated that climate change is the greatest single threat to national security, even greater than terrorism, because it will increase global instability. How much better to avoid these problems, particularly when doing so will create a better and more sustainable society?
Comment by: PT (David Alexander) (Oct-22-2007) Web site
It is about time that we can see a clear set of answers to these "myths" that keep popping up. Sometimes the questioner is sincere and simply repeating what he/she has read elsewhere, and sometimes it is from an individual who has spent a lot of time debating climate issues but has never made an effort to look into these questions and get answers, and simply wants to claim there is no evidence for AGW, without doing the research first. In either case, these questions need to be answered. Thank you, John!
Specialist in climatology and remote sensing. Current research interests are sea ice in the Arctic and influences on the occurrence of severe weather in the High Plains.
Fossil Fuel
jfheinrichs
In cooperation with PlanetThoughts.org, I have conducted this interview between myself and a composite, typical Anthropogenic Global Warming skeptic. That is to say, these are my answers to the questions and doubts typically posed (in many online discussions as well as at open meetings) by those who doubt that humans are causing the planet to become significantly warmer. We felt that this interview format of presentation would be more engaging, and more clear, than simply expounding a series of facts in a vacuum.
PT (David Alexander)
