We value your feedback Help us improve our content Your Email Address. Security code. Monitoring Greenhouse Gases in Antarctic Snow. Climate Change: Annual greenhouse gas index. Greenhouse Gas Concentrations - Graphing Tool. Climate Forcing. Air - Atmospheric Climate Variables. Greenhouse Gases: A Closer Look. Catching a Heat Wave. Finally, although rising CO 2 can stimulate plant growth, research has shown that it can also reduce the nutritional value of most food crops by reducing the concentrations of protein and essential minerals in most plant species.
Climate change can cause new patterns of pests and diseases to emerge, affecting plants, animals and humans, and posing new risks for food security, food safety and human health. In its Fifth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1, independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 95 percent probability that human activities over the past 50 years have warmed our planet.
The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from parts per million to about parts per million in the last years. The panel also concluded there's a better than 95 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past plus years.
It's reasonable to assume that changes in the Sun's energy output would cause the climate to change, since the Sun is the fundamental source of energy that drives our climate system. Indeed, studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity coupled with an increase in volcanic activity is thought to have helped trigger the Little Ice Age between approximately and , when Greenland cooled from to the s and glaciers advanced in the Alps.
But several lines of evidence show that current global warming cannot be explained by changes in energy from the Sun:. Not enough greenhouse effect: The planet Mars has a very thin atmosphere, nearly all carbon dioxide. Because of the low atmospheric pressure, and with little to no methane or water vapor to reinforce the weak greenhouse effect, Mars has a largely frozen surface that shows no evidence of life.
Too much greenhouse effect: The atmosphere of Venus, like Mars, is nearly all carbon dioxide. But Venus has about , times as much carbon dioxide in its atmosphere as Earth and about 19, times as much as Mars does , producing a runaway greenhouse effect and a surface temperature hot enough to melt lead.
The above graph compares global surface temperature changes red line and the Sun's energy that Earth receives yellow line in watts units of energy per square meter since We're the ones who burn fossil fuels, produce livestock and clear trees, increasing the amount of heat-trapping gases in the atmosphere.
No one questions the link between smoking and cancer, because the science was settled in the s after more than 50 years of research. We can think of the state of human activities and climate change as no different than smoking and cancer. In fact, we are as confident that humans cause climate change as we are that smoking causes cancer.
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