The IPCC also concludes that variations in natural phenomena such as solar radiation and volcanic eruptions had a small cooling effect after 1950. These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost nd sea ice. Other likely effects include changes in the frequency and intensity of extreme weather events, species extinctions, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional variations is uncertain. The main impact of global warming is climatic changes. Impact of global warming Effects on weather Increasing temperature is likely to lead to increasing precipitation but the effects on storms are less clear. Extratropical storms partly depend on the temperature gradient, which is predicted to weaken in the northern emisphere as the polar region warms more than the rest of the hemisphere. Extreme weather IPCC predicted that in the future, over most land areas, the frequency of warm spells or heat waves would very likely increase. Other likely changes are listed below: •Increased areas will be affected by drought •There will be increased intense tropical cyclone activity •There will be increased incidences of extreme high sea level (excluding tsunamis) Acidification Dissolving CO2 in seawater increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH. Caldeira and

Wickett (2003) placed the rate and magnitude of modern ocean acidification changes in the context of probable historical changes during the last 300 million years. Since the industrial revolution began, it is estimated that surface ocean pH has dropped by slightly less than 0. 1 units (on the logarithmic scale of pH; approximately a 25% increase in H+), and it is estimated that it will drop by a further 0. 3 to 0. 5 units by 2100 as the oceans absorb more anthropogenic CO2. Oxygen depletion The amount of oxygen dissolved in the oceans may decline, with adverse consequences for ocean life.

Oceans The role of the oceans in global warming is a complex one. The oceans serve as a sink for carbon dioxide, taking up much that would otherwise remain in the atmosphere, but increased levels of CO2 have led to ocean acidification. Furthermore, as the temperature of the oceans increases, they become less able to absorb excess CO2. Global warming is projected to have a number of effects on the oceans. Ongoing effects include rising sea levels due to thermal expansion and melting of glaciers and ice sheets, and warming of the ocean surface, leading to increased temperature stratification.

Other possible effects include large-scale changes in ocean circulation Current sea leve rise Current sea level rise has occurred at a mean rate of 1. 8 mm per year for the past century, and more recently, during the satellite era of sea level measurement, at rates estimated near 2. 8 ± 0. 4 to 3. 1 ± 0. 7 mm per year (1993-2003). Current sea level rise is due significantly to global warming, which will increase sea level over the coming century and longer periods. Increasing temperatures result in sea level rise by the thermal expansion of water and through the addition of water to the oceans from the elting of continental ice sheets. At the end of the 20th century, thermal expansion and melting of land ice contributed roughly equally to sea level rise, while thermal expansion is expected to contribute more than half of the rise in the upcoming century. Values for predicted sea level rise over the course of this century typically range from 90 to 880 mm, with a central value of 480 mm. Models of glacial flow give a theoretical maximum value for sea level rise in the current century of 2 metres (and a "more plausible" one of 0. 8 metres), based on limitations on how quickly ice can flow.

In general, low-latitude areas are at most risk of having decreased crop yields . About 1 to 3°C global mean temperature increase (by 2100, relative to the 1990-2000 average level) there would be productivity decreases for some cereals in low latitudes, and productivity increases in high latitudes. Water resources The negative impacts of climate change on freshwater systems outweigh the benefits. All of the regions assessed in the IPCC Fourth Assessment Report (Africa, Asia, Australia and New Zealand, Europe, Latin America, North America, Polar regions (Arctic and Antarctic), and small slands) showed an overall net negative impact of climate change on water resources and freshwater ecosystems. Semi-arid and arid areas are particularly exposed to the impacts of climate change on freshwate

Rising Ocean Levels ?The ocean could rise as much as one meter in this century, due to melting in the polar ice caps. ?This may not sound like much, but the repercussions are huge. ?Millions of people in crowded costal areas like Bangladesh, Shanghai, even Florida and Manhattan will be forced to relocate as these areas become uninhabitable. 40-50% of costal wetlands could be wiped out, killing off plant and animal species and leaving inland areas more susceptible to storms like hurricanes and tsunamis Coral Reef Bleaching •Change in temperature and elevated sea level cause loss of lgae in the coral. •Coral appears white, or “bleached. ” Result is mass death of sea animals, which are dependent on the coral reef Solution ?Plant trees ?Conserve energy-- 1. use low-energy, low-water-use washing machines, 2. use a solar heated system for hot water ?Buy energy efficient products ?Buy products that have reusable or recyclable packaging ?Reduce use of car ? To stabilize the climate at its present level, we must cut greenhouse gas emissions by 70%. ?Most experts believe there is still time to avoid drastic climate change. Conclusion