Climate Change Effects

1. How serious is a warming of a few degrees?
   The Intergovernmental Panel on Climate Change (IPCC) estimates it has warmed 1.2 to 1.4°F (0.7 to 0.8ºC) over the past century and projects a further 3 to 7°F (2 to 4ºC) over the 21st century. The increases may appear minor compared to short-term weather changes from night to day and winter to summer. In global climate terms, however, warming at this rate would be much larger and faster than any of the climate changes over at least the past 10,000 years.
2. Will a warming climate have more positive or negative effects?
   A warming climate will have both positive and negative impacts. Local impacts are the most difficult to predict, making it a challenge to know exactly who or what will be harmed or benefit. Generally, the risk of negative impacts from climate change increases the faster it warms. More rapid climate change makes adapting to change more difficult and costly. This is especially true for vulnerable groups (such as the poor, the very young, and older adults) and fragile ecosystems which may struggle to adapt to even small changes. The Intergovernmental Panel on Climate Change (IPCC) suggests that temperature increases above the range of 3.5 to 5.5°F (2 to 3ºC) over the next 100 years would dramatically increase the negative impacts of climate change. So a major aim of climate action is to reduce the risk and likelihood of large, rapid warming. 
3. How will climate change affect ecosystems? Some ecosystems have already been affected by changes in climate. As the climate continues to warm, major changes may occur in ecosystem structure and function, species’ ecological interactions, and species’ geographic ranges, with predominantly negative consequences for biodiversity. Warmer temperatures and precipitation changes will likely affect the habitats and migratory patterns of many types of wildlife. The range and distribution of many species will change, and some species that cannot move or adapt may face extinction. In addition, climate changes such as increased floods and droughts are predicted to increase the risk of extinction for some plant and animal species, many of which are already at-risk due to other non-climate related factors.
4. How will climate change affect human health? Longer, more intense and frequent heat waves may cause more heat-related death and illness. There is virtual certainty of declining air quality in cities since greater heat can also worsen air pollution such as ozone or smog. Insect-borne illnesses are also likely to increase as many insect ranges expand. Climate change health effects are especially serious for the very young, very old, or for those with heart and respiratory problems. Conversely, warmer winter temperatures may reduce the negative health impacts from cold weather.
5. How will climate change affect agriculture? The supply and cost of food may change as farmers and the food industry adapt to new climate patterns. A small amount of warming coupled with increasing CO₂ may benefit certain crops, plants, and forests, although the impacts of vegetation depend also on the availability of water and nutrients. For warming of more than a few degrees, the effects are expected to become increasingly negative, especially for vegetation near the warm end of its suitable range.
   
6. How will climate change affect polar regions? Polar regions are expected to warm more than any other parts of the world. In part, this is because ice has greater reflectivity (also known as albedo) than ocean or land. Melting of highly reflective snow and ice reveals darker land and ocean surfaces, which increases absorption of the sun’s heat and further warms the planet, especially in those regions. Polar ice sheets (such as those on Greenland and Antarctica) are some of the largest surface features on our planet. Any changes to them, however small, could have far-reaching effects. Polar ice sheets potentially will accumulate more snow and ice because of an increase in precipitation. However, overall melting due to global warming is expected to reduce the size and extent of the polar ice sheets. Melting of polar ice and land-based glaciers is expected to contribute to sea level rise. In addition to the ice sheets, sea ice is also melting. Though the melting of floating sea ice that covers part of the Arctic Ocean does not effect sea level, sea ice is important for wildlife and for keeping the region cool by reflecting sunlight back to space. If the Arctic loses the reflective surface of ice and then the dark Arctic Ocean absorbs more heat, the northern regions may warm even more rapidly.
   
7. How will a warming climate affect precipitation? Rising temperatures will intensify the Earth’s water cycle. Increased evaporation will make more water available in the air for storms, but contribute to drying over some land areas. As a result, storm-affected areas are likely to experience increases in precipitation and increased risk of flooding. But areas located far away from storm tracks are likely to experience less precipitation and increased risk of drought. In the U.S., warming is expected to cause a northward shift in storm tracks, resulting in decreases in precipitation in areas such as the Southwest U.S. but increases in many areas to the north and east. However, these changes will vary by season and depend on weather fluctuations.
8. How will climate change affect sea level? Sea levels are rising worldwide and along much of the U.S. coast. Tide gauge measurements and satellite altimetry suggest that sea level has risen worldwide approximately 4.8-8.8 inches (0.12-0.22 m) during the last century. A significant amount of sea level rise has likely resulted from the observed warming of the atmosphere and the oceans. The primary factors driving current sea level rise include the expansion of ocean water caused by warmer ocean temperatures (warmer water is less dense), melting of mountain glaciers and small ice caps (resulting in more water in the oceans and less on land), and - to a lesser extent - the melting of the Greenland Ice Sheet and the Antarctic Ice Sheet. The Intergovernmental Panel on Climate Change (IPCC) projects a six-inch to two-foot (0.18-0.59 m) rise in sea level during the 21st century. Sea level rise may be greater if there are sudden increases in ice sheet melt. Such increases have already been observed but their effects have not yet been incorporated into current projections of sea level rise. The stability of the West Antarctic Ice Sheet is of particular concern. A sudden collapse of the ice sheet could raise sea levels 16 to 20 feet (5-6 m). The IPCC is unable to estimate the likelihood or timing of such a collapse, however, due to incomplete understanding of all the processes affecting this ice sheet.
   
9. Will a warming climate make temperatures more extreme? Most scientists think that a warming climate will alter the frequency and severity of extreme temperature events. In general, they expect increases in heat waves and decreases in cold spells. These effects will vary from place to place.
10. How will a warming climate affect hurricanes? Because warm sea surface temperatures energize hurricanes, a warming climate is likely to make hurricanes more intense. Hurricanes in the future will probably have stronger peak winds and increased rainfall. The relationship between sea surface temperatures and the frequency of hurricanes is less clear. There is currently no scientific consensus on how a warming climate is likely to affect the frequency of hurricanes, but research continues.
11. How will climate change affect water resources? In a warming climate, extreme events like floods and droughts are likely to become more frequent. More frequent floods and droughts will affect water quality and availability. For example, increases in drought in some areas may increase the frequency of water shortages and lead to more restrictions on water usage. An overall increase in precipitation may increase water availability in some regions, but also create greater flood potential.
    
12. How will climate change affect coasts?
    If you live along the coast, your home may be impacted by sea level rise and an increase in storm intensity. Rising seas may contribute to enhanced coastal erosion, coastal flooding, loss of coastal wetlands, and increased risk of property loss from storm surges.
13. How will climate change affect energy? Warmer temperatures may result in higher energy bills for air conditioning in summer, and lower bills for heating in winter. Energy usage is also connected to water needs. Energy is needed for irrigation, which will most likely increase due to climate change. Also, energy is generated by hydropower in some regions, which will also be impacted by changing precipitation patterns.
    
14. How will climate change affect recreational opportunities? Some outdoor activities may benefit from longer periods of warm weather. However, many other outdoor activities could be compromised by increased beach erosion, increased heat waves, decreased snowfall, retreating glaciers, reduced biodiversity, and changing wildlife habitats.