Most climate scientists agree current global warming is from the human-caused increasing greenhouse effect of the atmosphere trapping heat from being released from Earth to space.
In the Climate Change 2014: Impacts, Adaptation, and Vulnerability report, the Intergovernmental Panel on Climate Change (IPCC) attributed a better than 95 percent chance that human activities are "the dominant cause of the observed warming" of the Earth's temperatures since the 1950s.
The projected effects of this increase are:
- Earth is becoming warmer on average, an improvement for some regions but a detriment to others.
- This will probably result in more evaporation and precipitation, but will vary with some regions dryer and some wetter.
- The oceans will warm, partially melt glaciers and other ice, and significantly expand rising sea levels.
- The Arctic Ocean will be ice-free in summer by mid-century instead of end of century as previously reported.
- Crops and plant life will respond differently to the changes. Some will grow better in the wetter or dryer conditions, increased carbon dioxide, and warmer temperatures while others will fail. Natural plants of regions will change.
The gases that do not respond to temperature changes stay semi-permanently in the atmosphere and are called climate change forcers, while ones like water that do respond are called feedbacks. Those causing the greenhouse effect are:
- water vapor--the most prevalent greenhouse gas increasing as the atmosphere warms along with clouds and precipitation, important feedbacks to the greenhouse effect.
- carbon dioxide (CO2)--the most important climate change forcer released naturally from volcanoes and respiration and human-caused actions like deforestation, changes in land use, and burning fossil fuels.
- Methane--a far more active hydrocarbon greenhouse gas than CO2 while less abundant in the atmosphere. It is produced naturally and is human-caused by landfill waste decomposition, domestic livestock digestion and manure, and agriculture choices, especially rice cultivation.
- nitrous oxide--human-caused by commercial and organic fertilizer, burning fossil fuels and biomass, producing nitric acid, and other soil cultivation methods.
- chlorofluorocarbons (CFCs)--synthetic industrial greenhouse gas compounds regulated now by international agreement because they destroy the ozone layer.
Changes in the sun's energy probably affected historical climate changes like the Little Ice Age from about 1650 to 1850 but cannot explain current global warming because:
- the average amount of solar energy has remained constant or increased only slightly since 1750. If the sun had more activity, then all atmospheric layers should be warmer. With greenhouse gasses trapping heat, the upper atmosphere has been cooling and the Earth's surface and lower atmosphere warming.
- climate models including solar irradiance changes are unable to reproduce the experienced 100 year temperature rise without a greenhouse gas rise as well.
The Earth's thermal blanket is what sustains life by absorbing heat and maintaining the average temperature of 59 degrees Fahrenheit. But it is a delicate balance that without controls on greenhouse gas emissions can destroy life.
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