All through Earth has warmed and cooled time and again when the planet received more or less sunlight but in the past century, another force has started to influence Earth's climate is humanity.
"Global warming is the rapid increase in Earth's average surface temperature over the past century primarily due to the greenhouse gases released as people burn fossil fuels."
The 30% of incoming sunlight is reflected back into space and remaining 70% is absorbed by the land and ocean, and the rest is absorbed by the atmosphere. This absorption and radiation of heat by the atmosphere—the natural greenhouse effect—is beneficial for life on Earth. If there were no greenhouse effect, the Earth's temperature would be -18°C (0°F) instead of the comfortable 15°C (59°F) that it is today.
Is Today's Warming Different from the Past?
Earth's past climates or "paleoclimates" reveals that the current climatic warming is occurring much more rapidly than past warming events. As the Earth moved out of ice ages, the global temperature raised 4-7°C over about 5,000 years. Models predict that Earth will warm between 2-6 degrees Celsius in the next century. The predicted rate of warming for the next century is at least 20 times faster.
Is Current Warming Natural?
Earth's climate changed due to wobbles in Earth's orbit, volcanic eruptions, ozone depletion etc. These natural causes are still in play today, but their influence is too small. NASA satellites record a vital signs including atmospheric aerosols (both from natural sources and human activities, such as factories, fires, deserts, and erupting volcanoes), atmospheric gases (including greenhouse gases), energy radiated from Earth's surface and the Sun, ocean surface temperature changes, global sea level, the extent of ice sheets, glaciers and sea ice, plant growth, rainfall, cloud structure, and more. The human influence on climate has eclipsed the magnitude of natural temperature changes over the past 120 years.
How Much More Will Earth Warm?
Scientists build climate models which are designed to simulate the responses and interactions of the oceans and atmosphere, and to account for changes to the land surface, both natural and human-induced. The models predict that as the world consumes ever more fossil fuel, greenhouse gas concentrations will continue to rise and Earth's average surface temperature will rise with them. Based on a range of plausible emission scenarios, average surface temperatures could raise between 2°C and 6°C by the end of the 21st century.
How Will Global Warming Change Earth?
Global warming will modifies rainfall patterns, amplifies coastal erosion, lengthens the growing season in some regions, melts ice caps and glaciers, and alters the ranges of some infectious diseases. Some of these changes are:
Changing Weather
Global warming will result in storms, floods, and droughts and hurricanes. With some exceptions, the tropics will likely receive less rain (orange) as the planet warms, while the Polar Regions will receive more precipitation (green).
Rising Sea Levels
Global warming will impact rising sea levels will erode coasts and cause frequent coastal flooding. Sea levels crept up about 20 cm during the twentieth century and predicted to go up 18-59 cm over the next century, though the increase could be greater if ice sheets in Greenland and Antarctica melt more quickly than predicted.
Impacting Ecosystems
Global warming is putting pressure on ecosystems, the plants and animals, both on land and in the ocean. Warmer temperatures may affect lifecycles of pollinators and plants to survive and reproduce, which would reduce food availability throughout the food chain. To survive the extreme temperatures, both marine and land-based plants and animals have started to migrate towards the poles. Those that cannot quickly migrate or adapt, face extinction. About 20-30% of plant and animal species will be at risk of extinction. if temperatures climb more than 1.5°-2.5°C.
Impacting People
As tropical temperature zones expand, the reach of some infectious diseases, such as malaria, will change. Rising sea levels will lead flooding and potential loss of property and life. Hotter summers and more frequent fires will lead to more cases of heat stroke and deaths. Intense droughts can lead to an increase in malnutrition. On a longer time scale, fresh water will become scarcer. The same small change in temperature, however, would reduce food production.
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