Q: Given a passage and a query based on the passage, generate an unambiguous, concise and simple answer to the query from information in the passage. Note that the answer may not be present in exact form.
The fact that 97 percent of climate experts agree on this subject also demonstrates the strength of the scientific evidence on human-caused global warming. And the strength of the evidence is why the IPCC is able to say with 95 percent confidence that humans are the main cause of the current global warming. These gases spread around the planet like a blanket, capturing the solar heat that would otherwise be radiated out into space. (For more detail on the basic mechanism of global warming, see carbon dioxide FAQ.) Both of these environmental problems do, however, have a common causehuman activities that release gases into and alter the atmosphere. Cooling from human aerosol emissions offsets about one-third of the warming from human greenhouse gas emissions. The new IPCC statement says that even taking that aerosol cooling effect into account, humans are still the main cause of the global warming over the past 60 years. Current Global Warming Caused by Greenhouse Gases, Not Nature. The IPCC elaborates further. What's causing global warming: human greenhouse gas emissions. With the evidence here and John's last post, you can bring it all together to make a pretty airtight logical proof for global warming. We know these things to be factually true: 1. Global temperatures have risen. 2. CO2 is a greenhouse gas. 3. CO2's concentration in the atmosphere has risen significantly. 4. 100 percent of the global warming over the past 60 years is human-caused, according to the IPCC's latest report. The IPCC is 95 percent confident that humans are the main cause of the current global warming. Photograph: Jianan Yu/Reuters The fifth Intergovernmental Panel on Climate Change (IPCC) report states with 95 percent confidence that humans are the main cause of the current global warming. Many media outlets have reported that this is an increase from the 90 percent certainty in the fourth IPCC report, but actually the change is much more significant than that. That is a lot different from saying that CO2 is the main cause of global warming. Never mind the possibility that you allude to about nuclear testing. Never mind the possibility that air pollution causes more clouds, and clouds as any farmer knows keeps things generally warmer. How do we know CO2 is causing warming? Posted on 8 October 2009 by John Cook. We've just perused the empirical evidence that humans are raising atmospheric CO2 levels. In earlier posts, we noted that tallying up the planet's heat content shows that our climate is accumulating heat, proof of global warming. But is there any evidence that links the two? How do we know that humans are the major cause of global warming? Photo: freeimage4life/Flickr We all know that warmingand coolinghas happened in the past, and long before humans were around. Many factors (called "climate drivers") can influence Earth's climatesuch as changes in the sun's intensity and volcanic eruptions, as well as heat-trapping gases in the atmosphere. Some of it makes its way back to the surface of the earth. Hence we expect to find increasing downward longwave radiation as CO2 levels increase. Philipona 2004 finds that this is indeed the case - that downward longwave radiation is increasing due to an enhanced . Evans 2006 takes this analysis further. So how do scientists know that today's warming is primarily caused by humans putting too much carbon in the atmosphere when we burn coal, oil, and gas or cut down forests? We know human activities are driving the increase in CO 2 concentrations because atmospheric CO 2 contains information about its source. Query: how do we know humans are the main cause for global warming
A:
The IPCC is 95 percent confident that humans are the main cause for global warming.