· Some parts of Earth are warming faster than others. But on average, global air temperatures near Earth's surface have gone up about 2 degrees Fahrenheit in the past years. In fact, the past five years have been the warmest five years in centuries. Many people, including scientists, are concerned about this warming Global warming is a phenomenon where the earth’s average temperature rises due to increased amounts of greenhouse gases. Greenhouse gases such as carbon dioxide, methane and ozone trap the incoming radiation from the sun. This effect creates a natural “blanket” which prevents the heat from escaping back into the atmosphere · Global warming is the long-term warming of the planet’s overall temperature. Though this warming trend has been going on for a long time, its pace has significantly increased in the last hundred years due to the burning of fossil fuels. As the human population has increased, so has the volume of fossil fuels burned
Global Warming | National Geographic Society
Throughout its long history, Earth has warmed and cooled small paragraph on global warming and again.
NASA astronaut photograph ISSE Earth has experienced climate change in the past without help from humanity. But the current climatic warming is occurring much more small paragraph on global warming than past warming events. These natural causes are still in play today, but their influence is too small or they occur too slowly to explain the rapid warming seen in recent decades.
Based on plausible emission scenarios, average surface temperatures could rise between 2°C and 6°C by the end of the 21st century. Some of this warming will occur even if future greenhouse gas emissions are reduced, because the Earth system has not yet fully adjusted to environmental changes we have already made. The impact of global warming is far greater than just increasing temperatures. Warming modifies rainfall patterns, amplifies coastal erosion, lengthens the growing season in some regions, small paragraph on global warming ice caps and glaciers, and alters the ranges of some infectious diseases.
Some of these changes small paragraph on global warming already occurring, small paragraph on global warming. How can we be certain that human-released greenhouse gases are causing the warming?
How much more will the Earth warm? How will Earth respond? Answering these questions is perhaps the most significant scientific challenge of our time.
The global average surface temperature rose 0. Temperatures are certain to go up further, small paragraph on global warming. Despite ups and downs from year to year, global average surface temperature is rising. NASA figure adapted from Goddard Institute for Space Studies Surface Temperature Analysis. Roughly 30 percent of incoming sunlight is reflected back into space by bright surfaces like clouds and ice.
Of the remaining 70 percent, most is absorbed by the land and ocean, and the rest is absorbed by the atmosphere. The absorbed solar energy heats our planet, small paragraph on global warming. From the surface, this energy travels into the atmosphere where much of it is absorbed by water vapor and long-lived greenhouse gases such as carbon dioxide and methane.
They radiate in all directions. The energy that radiates back toward Earth heats both the lower atmosphere and the surface, enhancing the heating they get from direct sunlight. This absorption and radiation of heat by the atmosphere—the natural greenhouse effect—is beneficial for life on Earth. What has scientists concerned now is that over the past years, humans have been artificially raising the concentration of greenhouse gases in the atmosphere at an ever-increasing rate, mostly by burning fossil fuels, small paragraph on global warming, but also from cutting down carbon-absorbing forests.
Since the Industrial Revolution began in aboutcarbon dioxide levels have increased nearly 38 percent as of and methane levels have increased percent. Increases in concentrations of carbon dioxide top and methane bottom coincided with the start of the Industrial Revolution in about Measurements from Antarctic ice cores green lines combined with direct atmospheric measurements blue lines show the increase of both gases over time.
NASA graphs by Robert Simmon, based on data from the NOAA Paleoclimatology and Earth System Research Laboratory. The atmosphere today contains more greenhouse gas molecules, so more of the infrared energy emitted by the surface ends up being absorbed by the atmosphere. We know about past climates because of evidence left in tree rings, small paragraph on global warming, layers of ice in glaciers, ocean sediments, coral reefs, and layers of sedimentary rocks. The chemical make-up of the ice provides clues to the average global temperature.
Earth has cycled between ice ages low points, large negative anomalies and warm interglacials peaks. NASA graph by Robert Simmon, based on data from Jouzel et al. But the paleoclimate record also reveals that the current climatic warming is occurring much more rapidly than past warming events. As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5, small paragraph on global warming, years.
In the past century alone, the temperature has climbed 0. Temperature histories from paleoclimate data green line compared to the history based on modern instruments blue line suggest that global temperature is warmer now than it has been in the past 1, years, and possibly longer. Graph adapted from Mann et al. Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5, years to warm 5 degrees.
The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual. Most often, global climate has changed because of variations in sunlight. Variations in the Sun itself have alternately increased and decreased the amount of solar energy reaching Earth.
Volcanic eruptions have generated particles that reflect sunlight, brightening the planet and cooling the climate. Volcanic activity has also, in the deep past, increased greenhouse gases over millions of years, contributing to episodes of global warming. We know this because scientists closely monitor the natural and human activities that influence climate with a fleet of satellites and surface instruments. Remote meteorological stations left and orbiting satellites right help scientists monitor the causes and effects of global small paragraph on global warming. On the ground, many agencies and nations support networks of weather and climate-monitoring stations that maintain temperature, rainfall, and snow depth records, and buoys that measure surface water and deep ocean temperatures.
Taken together, these measurements provide an ever-improving record of both natural events and human activity for the past years. Scientists integrate these measurements into climate models to recreate temperatures recorded over the past years. Climate model simulations that consider only natural solar variability and volcanic aerosols since —omitting observed increases in greenhouse gases—are able to fit the observations of global temperatures only up until about After that point, the decadal trend in global surface warming cannot be explained without including the contribution of the greenhouse gases added by humans.
For example, two major volcanic eruptions, El Chichon in and Pinatubo inpumped sulfur dioxide gas high into the atmosphere. Temperatures across the globe dipped for two to three years. Natural influences on temperature—El Niño, solar variability, and volcanic small paragraph on global warming varied approximately plus and minus 0.
Graphs adapted from Small paragraph on global warming et al. Although volcanoes are active around the world, and continue to emit carbon dioxide as they did in the past, the amount of carbon dioxide they release is extremely small compared to human emissions. On average, volcanoes emit between and million tonnes of carbon dioxide per year. By burning fossil fuels, people release in excess of times more, about 26 billion tonnes of carbon dioxide, into the atmosphere every year as of As a result, human activity overshadows any contribution volcanoes may have made to recent global warming.
Changes in the brightness of the Sun can influence the climate from decade to decade, small paragraph on global warming, but an increase in solar output falls short as an explanation for recent warming. The total energy the Sun radiates varies over an year cycle. During solar maxima, solar energy is approximately 0. The transparent halo known as the solar corona changes between solar maximum left and solar minimum right.
NASA Extreme Ultraviolet Telescope images from the SOHO Data Archive, small paragraph on global warming. Each cycle exhibits subtle differences in intensity and duration. As of earlythe solar brightness since has been slightly lower, not higher, than it was during the previous year minimum in solar activity, small paragraph on global warming, which occurred in the late s.
Satellite measurements of daily light line and monthly average dark line total solar irradiance since have not detected a clear long-term trend. NASA graph by Robert Simmon, based on data from the ACRIM Science Team. Scientists theorize that there may be a multi-decadal trend in solar output, though if one exists, it has not been observed as yet.
Even if the Sun were getting brighter, however, the pattern of warming observed on Earth since does not match the type of warming the Sun alone would cause. Satellite measurements show warming in the troposphere lower atmosphere, green line but cooling in the stratosphere upper atmosphere, small paragraph on global warming, red line. This vertical pattern is consistent with global warming due to increasing greenhouse gases, small paragraph on global warming, but inconsistent with warming from natural causes.
Graph by Robert Simmon, based on data from Remote Sensing Systems, sponsored by the NOAA Climate and Global Change Program. The stratosphere gets warmer during solar maxima because the ozone layer absorbs ultraviolet light; more ultraviolet light during solar maxima means warmer temperatures. Increased concentrations of carbon dioxide in the troposphere and stratosphere together contribute to cooling in the stratosphere. To further explore the causes and effects of global warming and to predict future warming, small paragraph on global warming, scientists build climate models—computer simulations of the climate system.
Climate models 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. Though the models are complicated, rigorous tests with real-world data hone small paragraph on global warming into powerful tools that allow scientists to explore our understanding of climate in ways not otherwise possible. Based on a range of plausible emission scenarios, average surface temperatures could rise between 2°C and 6°C by the end of the 21st century.
Model simulations by the Intergovernmental Panel on Climate Change estimate that Earth will warm between two and six degrees Celsius over the next century, depending on how fast carbon dioxide emissions grow. Scenarios that assume that people will burn more and more fossil fuel provide the estimates in the top end of the temperature range, while scenarios that assume that greenhouse gas emissions will grow slowly give lower temperature predictions.
The orange line provides an estimate of global temperatures if greenhouse gases stayed at year levels. Greenhouse gases are only part of the story when it comes to global warming. Changes to one part of the climate system can cause additional changes to the way the planet absorbs or reflects energy.
These secondary changes are called climate feedbacks, and they could more than double the amount of warming caused by carbon dioxide alone. The primary feedbacks are due to snow and ice, water vapor, clouds, and the carbon cycle. Perhaps the most well known feedback comes from melting snow and ice in the Northern Hemisphere. Warming temperatures are already melting a growing percentage of Arctic sea ice, exposing dark ocean water during the perpetual sunlight of summer. Snow cover on land is also dwindling in many areas.
In the absence of snow and ice, these areas go from having bright, sunlight-reflecting surfaces that cool the planet to having dark, sunlight-absorbing surfaces that bring more energy into the Earth system and cause more warming. In the past years, the glacier has lost half its volume and has retreated more than 1.
As glaciers retreat, sea ice disappears, and snow melts earlier in the spring, the Earth absorbs more sunlight than it would if the reflective snow and ice remained. Photograph © Hugh Saxby.
The largest feedback is water vapor. Water vapor is a strong greenhouse gas.
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, time: 1:33What Is Climate Change? | NASA Climate Kids
· Global warming is the long-term warming of the planet’s overall temperature. Though this warming trend has been going on for a long time, its pace has significantly increased in the last hundred years due to the burning of fossil fuels. As the human population has increased, so has the volume of fossil fuels burned Global warming is a phenomenon where the earth’s average temperature rises due to increased amounts of greenhouse gases. Greenhouse gases such as carbon dioxide, methane and ozone trap the incoming radiation from the sun. This effect creates a natural “blanket” which prevents the heat from escaping back into the atmosphere Global warming has led to a change in climatic conditions. There are droughts at some places and floods at some. This climatic imbalance is the result of global warming. Spread of Diseases. Global warming leads to a change in the patterns of heat and humidity. This has led to the movement of mosquitoes that carry and spread diseases. High Mortality Rates
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