PART 2: If climate changes what might happen?

Obviously, climate has a big influence on plants and animals in the natural environment, on oceans, and on human activities, such as agriculture, water supplies, and heating and cooling. The effects of climate change depend upon how much change there is, how fast it occurs, and how easily the world can adapt to the new conditions.

Impacts on people.
The effects of climate change on people would change a lot from place-to-place. Economically developed societies, like those in North America, Europe and Japan, could use technology to reduce direct impacts. For example, they might develop new crop varieties, construct new water systems, and limit coastal development. Some northern countries, such as Canada and Russia, might even benefit from longer growing seasons and lower heating bills if the climate becomes warmer.

In contrast, economically less developed societies, like those in parts of Africa, Asia, and South America depend much more directly on climate, and could be hit much harder by sudden or large changes. Places like coastal Bangladesh and low-lying islands, could be flooded by storms or rising sea level. Droughts in Africa might become more serious. Developing countries have far fewer resources for adapting to such changes. They may not be able to afford large projects such as sea walls or aqueducts. Peasant farmers may have difficulty adopting new agricultural practices. The resulting social tensions could lead to more political unrest, large-scale migrations, and serious international problems such as terrorism and wars.

Impacts on nature.
When scientists look at the past they find the natural environment has often adapted to climate changes that have occurred gradually over many thousands of years. However, they also find instances in which changes have occurred rapidly, brought about by events such as sudden shifts in ocean currents. These rapid changes have often caused widespread species extinctions and the collapse of natural ecosystems.

One way to understand the importance of the speed of change is to think about native plants that grow in North America. Global warming could mean that those currently growing in Georgia might be better suited to New England. If climate changes gradually, many plants may be able to "migrate" by spreading seeds into new areas where they can now grow. But if climate changes rapidly, many plants may not be able to spread their seeds far enough to reach the new area. If they die out, so may many of the animals that depend upon them.

Why do scientist disagree about possible impacts of climate change?
Scientists disagree about whether climate change will be a serious problem in the next 50 to 100 years. The main reason for this disagreement is that nobody knows for sure whether climate changes caused by human actions will be large enough and fast enough to cause serious damage. Many scientists believe that they may be. Others argue that if changes occur, the problems they cause will be minor compared with problems caused by today's storms and droughts. You can learn more about these disagreements and the possibility that scientists will be able to resolve them through research, in Details Booklet Part 2.

Will more carbon dioxide in the atmosphere cause trees and other plants to grow more?
It might. Plants need carbon dioxide to grow. Using sunlight and photosynthesis, plants change carbon dioxide and water into food. If plants have all the nutrients they need, then giving them more carbon dioxide will cause many to grow more. Commercial growers often do this in greenhouses. However, plants growing in natural environments often do not have all the nutrients they need, and may not grow faster, even if there is more carbon dioxide. If some plants on land and in the oceans are naturally able to take more carbon dioxide out of the atmosphere, they will grow faster. This would change the mix of plants, but might also slow global warming. You can learn more in Details Booklet Part 2.

Sea level rise and coastal storms.
Most of the rise in sea level would occur because water expands when it is heated. An increase in the earth's average temperature of about 3.5°F, which is probably too little to melt most polar ice, would result in an increase in sea level of between 8 and 30 inches. This is too little to flood most coastal cities, but could damage some coastal plants and animals, beaches, and water supplies. While flooding under normal weather conditions might be small, higher sea level would mean that hurricanes and similar large storms could do more damage than in the past. Some experts argue that such storms would become more frequent and intense in a warmer climate. This could have large impacts. Other experts doubt such changes will occur.

Examples of how large and rapid climate change might affect the natural environment.

Plant migration: Climate may change faster than plants can move from one region to another. This may cause species extinction, lower biodiversity, and changes in the way species interact.

Coral reefs: Slightly warmer tropical water may kill the algae which reef animals use for food.

Changes in insect pests: Climate change can affect the number and kinds of pests directly. It can also affect them by changing the mix of plant varieties and their nutrient content. This can influence plant survival, food chains, and the spread of disease.

Mangrove swamps: Mangrove swamps are important breeding grounds for many animals that live in water. Increased ocean flooding may damage these areas by changing the supply of nutrients and the amount of salt.