The changing global climate is already affecting—and will continue to affect—people and the environment in many ways. Following is a summary of some of the projected effects.
The crops that we grow for food need specific conditions to thrive, including the right temperature and enough water. A changing climate could have both positive and negative effects on crops. For example, the northern parts of the United States have generally cool temperatures, so warmer weather could help certain crops grow. In southern areas where temperatures are already hot, even more heat could hurt crop growth.
Global temperature changes will affect how much energy we need and when we need it. As temperatures rise, more people will need to keep cool by using air conditioning, which uses a lot of electricity. However, some people might need less energy to heat buildings in the winter because it may not get as cold as it used to be. Climate change could also make it harder to produce certain types of electricity, such as hydropower, because a drier climate will result in lower water levels in rivers and reduce the rivers’ ability to generate electricity.
Heat waves, severe storms, air pollution, and diseases linked to climate already threaten people’s health in many areas of the world. A changing climate will increase these threats. Some people will be particularly at risk, including those who are poor, very young or elderly, or disabled, or those who live in coastal areas or big cities.
The changing climate might also allow some infectious diseases to spread. As winter temperatures increase, ticks and mosquitoes that carry diseases will be able to survive longer throughout the year and expand their ranges, putting more people at risk. One big concern is malaria, a deadly disease spread by mosquitoes in many hot, humid parts of the world.
Climate change is affecting where, when, and how much water is available for people to use. Many parts of the world already have very little water, and this problem may worsen. Rising temperatures, changing precipitation patterns, and increasing droughts will affect the amount of water in lakes, rivers, and streams, as well as the amount of water that seeps into the ground to replenish groundwater.
Plants, Animals, and Ecosystems
Most plants and animals live in areas with very specific climate conditions, such as temperature and rainfall patterns, that enable them to thrive. Any change in the climate of an area can affect the plants and animals living there, as well as the makeup of the entire ecosystem. Some species are already responding to a warmer climate by moving to cooler locations. For example, some North American animals and plants are moving farther north or to higher elevations to find suitable places to live. Climate change also alters the life cycles of plants and animals. For example, as temperatures get warmer, many plants are starting to grow and bloom earlier in the spring and survive longer into the fall. Some animals are also waking from hibernation sooner or migrating at different times.
Forests provide homes for many kinds of plants and animals. They also protect water quality, offer opportunities for recreation, and provide people with wood. Forests are sensitive to many effects of climate change, including shifting weather patterns, drought, wildfires, and the spread of pests like the mountain pine beetle. Unlike some animals, trees can’t move when the temperature gets too hot or other conditions change. (For information about projected changes in specific forest regions, see the Regional Trends and Projections student page.)
What People Are Doing
Scientists, industry, citizens, and government officials do not always agree on what should be done regarding levels of greenhouse gases and global climate change. For example, some believe we should do everything we can to curtail CO2 emissions, while others believe that approach could have serious economic consequences.
However, many countries, organizations, and individuals around the world have already taken steps to reduce their emissions of CO2 and other greenhouse gases in ways that support their economies. Methods to reduce CO2 emissions include increasing the efficiency of various appliances and using different sources of energy that add few or no emissions to the atmosphere (including solar, hydropower, wind, and geothermal energy). Since each energy source has its own drawbacks and limitations, some industries propose to use a “mix” of energy types, including some fossil fuels and some renewable energy sources.
Meanwhile, we can examine our individual energy use and make efforts to reduce our own contributions to greenhouse gas emissions by being conscious of our energy use at home, at school, and on the road. A carbon footprint is a measurement of how much CO2 one organization, person, or product produces—directly or indirectly—over a defined period of time (usually one year). The measure is an indication of the effect on CO2 levels of that organization, person, or product.
1. What are the projected positive and negative effects of climate change on agriculture? On energy? On human health? On water supplies?
2. How are forest trees different from other plants and animals in their ability to respond to climate changes?
3. What things can people do to reduce CO2 emissions?