NASA’s article begins down below:
Most climate scientists agree the main cause of the current global warming trend is human expansion of the “greenhouse effect”1 — warming that results when the atmosphere traps heat radiating from Earth toward space.
On Earth, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2. To a lesser extent, the clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases.
The consequences of changing the natural atmospheric greenhouse are difficult to predict, but certain effects seem likely:
The 2nd billet above is so very true and a perfect example of that is Yosemite National Forest. Thanks to years worth of drought caused by climate change, this decades (or centuries) old forest is now being decimated. Hopefully the Park service or mother nature will take down a lot of these dead trees by means of wind or ice otherwise this is fuel for a wicked wild fire.
In its Fourth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there’s a more than 90 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 280 parts per million to 400 parts per million in the last 150 years. The panel also concluded there’s a better than 90 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 50 years.
They said the rate of increase in global warming due to these gases is very likely to be unprecedented within the past 10,000 years or more. The panel’s full Summary for Policymakers report is online at http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf.
There’s more info at NASA’s link but this is the meat and potatoes of it all. If you wanna read more go here.