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Re: Questions on Global Warming

An 8th Grader Asks About Global Warming
Henry Hengeveld, Senior Advisor with Environment Canada, replies



Date: Sun, 18 Feb 2001 5:49 PM
To: publisher@naturalscience.com
Subject: Questions on Global Warming


Questions on Global Warming

Hi! my name is Katie. I am an 8th grade student and I have to do a big project called "exploration". It's a science research project and the topic I have chosen is global warming. I must have 8 valid sources for this project and one of them has to be an interview. I was just wondering if you could answer the questions on global warming that I have listed below.

Katie



The Interview (We passed Katie's request for an interview to Henry Hengeveld, Senior Science Advisor on Climate Change, with the Meteorological Service of Canada, who kindly provided these answers.)

Katie: What is global warming?

Henry Hengeveld: In scientific terms, global warming refers to any processes that causes the earth's average surface temperatures to increase over time. However, during the past decade, the term global warming has frequently been used to describe the effect of human emissions of greenhouse gases into the atmosphere, which increases the amount of energy trapped near the earth's surface and causes average temperatures to rise. Since the temperature increases are not uniform around the world, global warming also causes weather circulation patterns to change and alters many other aspects of our climate and weather. That is why experts and policy makers now refer to this process as climate change, not just global warming.

Katie: What changes in weather patterns are indicative of global warming?

Henry Hengeveld: A warmer world due to human emissions of greenhouse gases will cause the polar regions to warm more than the tropics. This decreases the temperature differences between the poles and the equator and reduces the forces that cause the strong westerly winds the flow from west to east in the mid-latitudes of the Northern Hemisphere. This in turn causes storm paths to change. In general, Canadian winters will likely be wetter than they are now, with more of the precipitation falling as rain. Our snow season will become shorter. In summer, much of southern Canada is expected to become drier, mainly because of higher evaporation due to warmer temperatures. In the north, it will likley become wetter. Summer storms are expected to be more intense, but when it becomes dry, the intensity of the drought is also likely to increase, again because of increased evaporation. In other words, the weather will be much different from what we would now expect.

Katie: Does El Nino have anything to do with global warming and if so how?

Henry Hengeveld: El Nino and La Nina are causes by a natural oscillation in the tropical ocean that causes surface waters in the eastern Pacific to alternately become much warmer (El Nino) or much colder (La Nina) than average. During El Nino, there is a significant increase in precipitation in the mid-Americas and further north into California, and weather patterns around the world get disrupted. The pattern of change is somewhat reversed during La Nina. In recent decades, the behaviour of El Ninos and La Ninas has changed from that in the earlier part of the 20th century, with more frequent and more intense El Nino events. This has affected our climates in recent years, but it is as yet unclear whether or not this shift in pattern is due to global climate change. Some models predict that a warmer world will look more like that of a typical El Nino year. Others suggest that both the intensity of El Nino and La Nina events will increase. Much more research is needed to properly address this question.

Katie: Do you think global warming is truly happening and if so do you think it will soon destroy earth?

Henry Hengeveld: In January, 2001, the lead experts from countries from all around the world met in China to provide the most up-to-date answer to these and other questions. They concluded that global warming is already happening. Temperatures have warmed by 0.6C during the past century, and the 20th century is now the warmest of the millennium, the 1990s the warmest decade and 1998 the single warmest year. Other evidence, like shrinking snow cover and sea ice, retreating glaciers, migrating insects and birds, changes in sea levels, etc are all consistent with these observations. Simulations with sophisticated climate models, the main tool used by researchers to study climate change, indicate that this warming will continue, with temperatures by 2100 being 1.4 to 5.8C warmer than today. Government programs to reduce our greenhouse emissions could help reduce this warming, but cannot stop it. Even very aggressive programs could still result in a warming of 2-3C. Global warming, however, is not likely to destroy the earth. The rate of warming expected is unprecedented in at least the past 10,000 years and will almost certainly cause much damage to ecosystems and society. This is particularly true for tropical regions and if the change is very rapid. However, some parts of the world will ultimately benefit from warmer growing seasons and milder climates, particularly once the climate has again stabilized. Canada is one of those areas. Some of the biggest long term concerns for Canada in terms of harm are dryer climates (and hence less water resources) in the south, sea level rise on the coasts, increased frequency of extreme weather, and, in the north, the effect of much warmer climates on sea ice, permafrost and wildlife dependent on these.

Katie: What areas are most effected by global warming and why?

Henry Hengeveld: Climate will change the most in polar regions, where it reduces snow and ice, which in turn increases the heating in the region. However, the greatest impacts are likely to be in tropical countries, on islands in the middle of the oceans, and in dry areas of the world. That is because many countries in the tropics are poor and cannot cope well with even small changes in weather and climate, small island states are seriously affected by even small changes in sea levels, and changes in precipitation in dry regions can cause much larger changes in stream run-off and hence in the risks of floods or droughts.

Katie: Is the hole in the ozone layer affecting global warming?

Henry Hengeveld: Ozone is also a greenhouse gas. Hence less ozone in the lower stratosphere due to the thinning of the ozone layer causes a surface cooling. Increased penetration of ultraviolet light into the lower atmosphere as the ozone thins helps to partially offset this cooling, but it is still significant. As the ozone layer heals due to the banning of the halon gases that cause ozone depletion, this modest cooling effect will slowly disappear.

Katie: If humans are the reasons for global warming how can we prevent it?

Henry Hengeveld: We can no longer prevent climate change, since it is already happening. However, we can slow it down and therefore buy ourselves time to prepare for the expected changes. The main way of doing this is by reducing greenhouse gas emissions. We can do that by being more energy efficient and by investing in technologies that will allow us to use cleaner renewable energies in the future. However, in addition to doing our part by being more energy efficient ourselves, we need to let both governments and industry know that we want them to reduce emissions. For government, the best way to communicate is by directly talking or writing to politicians and by how we vote. For industry, it is important to let them know that we want energy efficient products, particularly cars.

Henry Hengeveld
Senior Science Advisor on Climate Change
Meteorological Service of Canada, Environment Canada
Downsview, Ontario. email: henryhengeveld@ec.gc.ca
URL: http://www.msc-smc.ec.gc.ca/saib/


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