Effects of global warming
The predicted effects of global warming for the environment and for human life are numerous and varied. The main effect is an increasing global average temperature. From this flow a variety of resulting effects, namely, rising sea levels, altered patterns of agriculture, increased extreme weather events, and the expansion of the range of tropical diseases. In some cases, the effects may already be occurring, although it is generally difficult to attribute specific natural phenomena to long-term global warming.
The extent and likelihood of these consequences is a matter of considerable political controversy; and in the details, a matter of some scientific uncertainty. A summary of possible effects and our current understanding can be found in the report of the IPCC Working Group II; a discussion of projected climate changes is found in WG I.
Proposed responses to the effects of global warming fall into two categories: mitigation and adaptation.
Projected climate changes due to global warming have the potential to lead to future large-scale and possibly irreversible changes in our climate resulting in impacts at continental and global scales.
Examples of projected climate changes include:
- significant slowing of the ocean circulation that transports warm water to the North Atlantic,
- large reductions in the Greenland and West Antarctic Ice Sheets,
- accelerated global warming due to carbon cycle feedbacks in the terrestrial biosphere, and
- releases of terrestrial carbon from permafrost regions and methane from hydrates in coastal sediments.
The likelihood of many of these changes is uncertain. However, the probability of one or more of these changes occurring is likely to increase with the rate, magnitude, and duration of climate change.
Scientists are unable to accurately predict when various effects of global warming will occur or what the magnitude of the effect will be.
It is not possible to be certain whether there will be any positive benefits of Global Warming. What is known is that some significant negative impacts are projected and these drive most of the concern about global warming and motivates attempts to mitigate or adapt to the effects of global warming.
Most of the consequences of global warming would result from one of three physical changes: sea level rise, higher local temperatures, and changes in rainfall patterns (Figure 1). Sea level is generally expected to rise 50-200 cm in the next century (Dean et al. 1987); such a rise would inundate 7,000 square miles of dry land in the United States (an area the size of Massachusetts) and a similar amount of coastal wetlands; erode recreational beaches 100-200 meters, exacerbate coastal flooding; and increase the salinity of aquifers and estuaries (Titus 1989).