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Impact of Continued Global Warming

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Impact of Continued Global Warming

“The Inuit see this and the world should know this...”

“It’s happening right before our eyes. If we’re going to be ignored, it’s like putting a shotgun in our mouth and pulling the trigger.” — 23-year-old Jordan Konek, one of the native people of the Canadian Arctic, to the 2011 Climate Change Conference in Durban, South Africa.

Future Warming

The amount CO 2 levels will rise in the next decades is unknown. What will this number depend on in the developed nations? What will it depend on in the developing nations? In the developed nations it will depend on technological advances or lifestyle changes that decrease emissions. In the developing nations, it will depend on how much their lifestyles improve and how these improvements are made.

If nothing is done to decrease the rate of CO 2 emissions, by 2030, CO 2 emissions are projected to be 63% greater than they were in 2002.

Global CO 2 emissions are rising rapidly. The industrial revolution began about 1850 and industrialization has been accelerating.

Temperature Scenarios

Computer models are used to predict the effects of greenhouse gas increases on climate for the planet as a whole and also for specific regions. If nothing is done to control greenhouse gas emissions and they continue to increase at current rates, the surface temperature of the Earth can be expected to increase between 0.5 o C and 2.0 o C (0.9 o F and 3.6 o F) by 2050 and between 2 o and 4.5 o C (3.5 o and 8 o F) by 2100, with CO 2 levels over 800 parts per million (ppm) ( Figure below ). On the other hand, if severe limits on CO 2 emissions begin soon, temperatures could rise less than 1.1 o C (2 o F) by 2100.

This video explores the tools NASA scientists use to determine how the climate is changing: http://www.youtube.com/watch?v=JRayIgKublg&feature=channel (4:00).

Various climate prediction models show how temperature is likely to rise by 2100.

Whatever the temperature increase, it will not be uniform around the globe. A rise of 2.8 o C (5 o F) would result in 0.6 o to 1.2 o C (1 o to 2 o F) at the equator, but up to 6.7 o C (12 o F) at the poles. So far, global warming has affected the North Pole more than the South Pole, but temperatures are still increasing at Antarctica ( Figure below ).

Temperature changes over Antarctica.

Animations of temperature anomalies for 5- and 10-year periods: http://data.giss.nasa.gov/gistemp/animations/ .

Global Changes

As greenhouse gases increase, changes will be more extreme. Oceans will become slightly more acidic, making it more difficult for creatures with carbonate shells to grow, and that includes coral reefs. A study monitoring ocean acidity in the Pacific Northwest found ocean acidity increasing ten times faster than expected and 10% to 20% of shellfish (mussels) being replaced by acid-tolerant algae.

Plant and animal species seeking cooler temperatures will need to move poleward 100 to 150 km (60 to 90 miles) or upward 150 m (500 feet) for each 1.0 o C (8 o F) rise in global temperature. There will be a tremendous loss of biodiversity because forest species can’t migrate that rapidly. Biologists have already documented the extinction of high-altitude species that have nowhere higher to go.

Decreased snow packs, shrinking glaciers, and the earlier arrival of spring will all lessen the amount of water available in some regions of the world, including the western United States and much of Asia. Ice will continue to melt and sea level is predicted to rise 18 to 97 cm (7 to 38 inches) by 2100 ( Figure below ). An increase this large will gradually flood coastal regions, where about one-third of the world's population lives, forcing billions of people to move inland.

Sea ice thickness around the North Pole has been decreasing in recent decades and will continue to decrease in the coming decades.

Weather will become more extreme, with more frequent and more intense heat waves and droughts. Some modelers predict that the midwestern United States will become too dry to support agriculture and that Canada will become the new breadbasket. In all, about 10% to 50% of current cropland worldwide may become unusable if CO 2 doubles.

Although scientists do not all agree, hurricanes are likely to become more severe and possibly more frequent. Tropical and subtropical insects will expand their ranges, resulting in the spread of tropical diseases such as malaria, encephalitis, yellow fever, and dengue fever.

You may notice that the numerical predictions above contain wide ranges. Sea level, for example, is expected to rise somewhere between 18 and 97 cm — quite a wide range. What is the reason for this uncertainty? It is partly because scientists cannot predict exactly how the Earth will respond to increased levels of greenhouses gases. How quickly greenhouse gases continue to build up in the atmosphere depends in part on the choices we make.

An important question people ask is this: Are the increases in global temperature natural? In other words, can natural variations in temperature account for the increase in temperature that we see? The answer is no. Changes in the Sun’s irradiance, El Niño and La Niña cycles, natural changes in greenhouse gas, and other atmospheric gases cannot account for the increase in temperature that has already happened in the past decades.

This video discusses how, by using the CERES satellite, scientists monitor energy in the atmosphere, including incoming solar energy and reflected and absorbed energy. Greenhouse warming that results from atmospheric greenhouse gasses is also monitored: http://www.youtube.com/watch?v=JFfD6jn_OvA (4:31).

Along with the rest of the world's oceans, San Francisco Bay is rising. Changes are happening slowly in the coastal arena of the San Francisco Bay Area and even the most optimistic estimates about how high and how quickly this rise will occur indicate potentially huge problems for the region.

Find out more at http://science.kqed.org/quest/video/going-up-sea-level-rise-in-san-francisco-bay/.

How Bad Could a Few Degrees Be?

How bad could a few degrees be? National Geographic has a set of videos about what to expect if temperature rises by each of these amounts by degree Celsius.

Summary

  • An increase in greenhouse gases will increase the changes that are already being seen including in ocean acidity.
  • A decrease in snow pack will cause a shortage of water in a lot of regions that depend on a summer melt to supply water in the dry months.
  • Temperature changes are not uniform around the globe. The largest changes are being seen in the polar regions.

Practice

Use this resource to answer the questions that follow.

NASA Global Climate Change - Effects

http://climate.nasa.gov/effects/

1. What is the evidence that climate change is occurring?

2. What do scientists expect to see in the coming decades?

3. What is the expected temperature change for the next century?

4. What changes are expected to be seen in North America?

5. What phenomenon is virtually certain to occur in the future?

Review

1. What does a computer model that predicts environmental changes due to increases in atmospheric greenhouse gases need to take into account?

2. Why does a small change in average global temperature have a large effect on the planet?

3. Why do you think that scientists do not have a firm understanding of how Earth will respond to increases in global temperature in the future?

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