Global climate change is Man-Made
Natural climate variability is extremely unlikely to have contributed more than about one-quarter of the temperature rise observed in the past 60 years, reports a pair of Swiss climate modelers in a paper published online December 4. Most of the observed warming—at least 74 percent—is almost certainly due to human activity, they write in Nature Geoscience.
Since 1950, the average global surface air temperature has increased by more than 0.5 degree Celsius. To separate human and natural causes of warming, the researchers analyzed changes in the balance of heat energy entering and leaving Earth—a new "attribution" method for understanding the physical causes of climate change.
Their findings, which are strikingly similar to results produced by other attribution methods, provide an alternative line of evidence that greenhouse gases, and in particular carbon dioxide, are by far the main culprit of recent global warming. The massive increase of atmospheric CO2 concentrations since pre-industrial times would, in fact, have caused substantially more surface warming were it not for the cooling effects of atmospheric aerosols such as black carbon, they report.
Previous attempts to disentangle anthropogenic and natural warming used a statistically complex technique called optimal fingerprinting to compare observed patterns of surface air temperature over time with the modeled climate response to greenhouse gases, solar radiation and aerosols from volcanoes and other sources.
"Optimal fingerprinting is a powerful technique, but to most people it’s a black box, " says Reto Knutti, a climate scientist at the Swiss Federal Institute of Technology (ETH) in Zurich, one of the authors of the report.
A balanced view
Knutti and his co-author Markus Huber, also at ETH Zurich, took a different approach. They utilized a much simpler model of Earth’s total energy budget and ran the model many thousands of times, using different combinations of a few crucial parameters that contribute to the energy budget. These included global values for incoming shortwave radiation from the Sun, solar energy leaving Earth, heat absorbed by the oceans and climate-feedback effects (such as reduced snow cover, which amplifies warming by exposing darker surfaces that absorb more heat).
What are the manmade causes for climate change?
Man has been burning fossil fuels in industry, transport and to generate electricity. This releases carbon dioxide that has been safely hidden underground for millions of years. This addition the the greenhouse gas levels is causing global warming, which is then the cause of climate change.
Deforestation is another cause, because trees remove carbon from the atmosphere.
Is global climate change man-made?
Yes it is. It's a by-product of burning fossil fuels, which release greenhouse gases, including Carbon Dioxide. It is also a side effect of deforestation and intensive livestock farming, which releases methane. In effect, our presence has resulted in a change in balance between the removal of greenhouse gases from the atmospehere and the production of greenhouse gases.
The science here is hardly settled. Many top scientists refute this idea of global warming. In fact, there have been times in the past, before the rise of industry, when the world was warmer than today.