Teach-in offers ideas to fight climate shift

Q&A from the Department of Ecology

Question: What is causing global warming?

Answer: Scientists have concluded that human activities are contributing to global warming by adding large amounts of heat-trapping gases to the atmosphere. Our fossil-fuel use is the main source of these gases. Every time we drive a car, use electricity from coal-fired power plants or heat our homes with oil or natural gas, we release carbon dioxide and other heat-trapping gases into the air. The second most important source of greenhouse gases is deforestation, mainly in the tropics, and other land-use changes.

As the concentration of these gases grows, more heat is trapped by the atmosphere and less escapes back into space. That increase in trapped heat changes the climate, causing altered weather patterns that can bring unusually intense precipitation or dry spells and more severe storms.

Q: Is global warming already happening?

A: An increasing body of observations gives a collective picture of a warming world:

• Increase in global average surface temperature of about 1 degree

• Decrease of snow cover and sea ice extent and the retreat of mountain glaciers

• Rise in global average sea level and increase in ocean water temperatures

• Likely increase in average precipitation in the middle and high latitudes of the Northern Hemisphere, and in tropical land areas

• Increase in the frequency of extreme precipitation events in some regions of the world

Examples of observed physical and ecological changes:

• Thawing of permafrost

• Lengthening of the growing season in middle and high latitudes

• Poleward and upward shift of plant and animal ranges

• Decline of some plant and animal species

• Earlier flowering of trees, earlier emergence of insects and earlier egg-laying in birds

Q: Are humans contributing to global warming?

A: Scientists have found evidence that leads to this conclusion:

• The observed warming for the past 100 years is unlikely to be because of natural causes alone; it was unusual even in the context of the past 1,000 years.

• There are better techniques to detect climatic changes and attribute them to different causes.

• Simulations of the climate's response to natural causes (sun, volcanoes, etc.) during the latter half of the 20th century alone cannot explain the observed trends.

• Most simulation models that take into account greenhouse-gas emissions and sulphate aerosols (which have a cooling effect) are consistent with observations the past 50 years.

Q: How much warmer is the earth likely to become?

A: The earth's average surface temperature will increase between 2.5 degrees and 10.4 degrees between 1990 and 2100 if no major efforts are undertaken to reduce the emissions of greenhouse gases.

Scientists predict that even if we stopped emitting heat-trapping gases immediately, the climate would not stabilize because the gases already released will stay there for years or even centuries. So while the warming might be lower or increase at a slower rate, global temperatures cannot quickly return to today's averages. The faster and more the earth warms, the greater the chances are for some irreversible climate changes.

Q: Would a temperature rise of a couple of degrees really change the global climate?

A: An increase of a few degrees won't simply make for pleasantly warmer temperatures around the globe. Even a modest rise of 2 degrees to 3 degrees could have dramatic effects. In the last 10,000 years, the earth's average temperature hasn't varied by more than 1.8 degrees. Temperatures only 5 degrees to 9 degrees cooler than today prevailed at the end of the last ice age, in which the northeast United States was covered by more than 3,000 feet of ice.

Scientists predict that continued global warming on the order of 2.5 degrees to 10.4 degrees during the next 100 years is likely to result in a rise in sea level between 3.5 inches and 34.6 inches, leading to:

• More coastal erosion, flooding during storms and permanent inundation of severe stress on many forests, wetlands, alpine regions and other natural ecosystems

• Greater threats to human health as mosquitoes and other disease-carrying insects and rodents spread diseases throughout larger geographical regions

• Disruption of agriculture in some parts of the world because of increased temperature, water stress and sea-level rise in low-lying areas such as Bangladesh or the Mississippi River delta.

Q: Is global warming connected with the hole in the ozone layer?

A: Global warming and ozone depletion are two separate but related threats. Global warming and the greenhouse effect refer to the warming of the lower part of the atmosphere because of increasing concentrations of heat-trapping gases. By contrast, the ozone hole refers to the loss of ozone in the upper part of the atmosphere. This is of serious concern because stratospheric ozone blocks incoming ultraviolet radiation from the sun, some of which is harmful to plants, animals and humans.

The problems are related in a number of ways. Some human-made gases, called chlorofluorocarbons, trap heat and destroy the ozone layer. Those gases are responsible for less than 10 percent of total atmospheric warming, far less than the contribution from the main greenhouse gas, carbon dioxide.

Q: Is there anything we can do about global warming?

A: Reduce emissions of heat-trapping gases.

Governments can adopt a range of options for reducing greenhouse-gas emissions, including:

• Increasing energy-efficiency standards

• Encouraging the use of renewable energy sources, such as wind and solar power

• Eliminating subsidies that encourage the use of coal and oil by making them artificially cheap

• Protecting and restoring forests, which serve as storehouses of carbon

Individuals can reduce the need for fossil fuels and often save money by:

• Driving less and driving more fuel-efficient and less-polluting cars

• Using energy-efficient appliances, insulating homes and using less electricity in general

Businesses can increase efficiency and save substantial sums by doing the same things on a larger scale.

Utilities can avoid building expensive new power plants by encouraging and helping customers to adopt efficiency measures.

Q: Will responding to global warming be harmful to the economy?

A: The challenge is to strike a balance between responding early enough to avoid major negative, costly effects, and responding sometime later to avoid taking big, expensive steps now that then could turn out to be unnecessary or inappropriate.

Global warming involves many unknowns, but the remaining uncertainties in our scientific understanding no longer warrant a "wait and see" stance. Science tells us with increasing certainty that we are in for a serious long-term problem.

There is much we can do that makes sense in terms of the economic bottom line while helping to reduce our effect on the global climate. The United States and other countries should seize the opportunity to take the lead in developing new, clean, energy-efficient technologies, and help developing countries take a greener path to economic prosperity.

All of that can be done in a cost-effective manner, while creating jobs and new business opportunities.