Global Warming: Natural or Manmade? Hentet fra Roy Spencer. Ph.D. Climatologist, author, former NASA scientist.

“Global warming” refers to the global-average temperature increase that has been observed over the last one hundred years or more. But to many politicians and the public, the term carries the implication that mankind is responsible for that warming. This website describes evidence from my group’s government-funded research that suggests global warming is mostly natural, and that the climate system is quite insensitive to humanity’s greenhouse gas emissions and aerosol pollution.

Believe it or not, very little research has ever been funded to search for natural mechanisms of warming…it has simply been assumed that global warming is manmade. This assumption is rather easy for scientists since we do not have enough accurate global data for a long enough period of time to see whether there are natural warming mechanisms at work.

The United Nation’s Intergovernmental Panel on Climate Change (IPCC) claims that the only way they can get their computerized climate models to produce the observed warming is with anthropogenic (human-caused) pollution. But they’re not going to find something if they don’t search for it. More than one scientist has asked me, “What else COULD it be?” Well, the answer to that takes a little digging… and as I show, one doesn’t have to dig very far.

But first let’s examine the basics of why so many scientists think global warming is manmade. Earth’s atmosphere contains natural greenhouse gases (mostly water vapor, carbon dioxide, and methane) which act to keep the lower layers of the atmosphere warmer than they otherwise would be without those gases. Greenhouse gases trap infrared radiation — the radiant heat energy that the Earth naturally emits to outer space in response to solar heating. Mankind’s burning of fossil fuels (mostly coal, petroleum, and natural gas) releases carbon dioxide into the atmosphere and this is believed to be enhancing the Earth’s natural greenhouse effect. As of 2008, the concentration of carbon dioxide in the atmosphere was about 40% to 45% higher than it was before the start of the industrial revolution in the 1800’s.

It is interesting to note that, even though carbon dioxide is necessary for life on Earth to exist, there is precious little of it in Earth’s atmosphere. As of 2008, only 39 out of every 100,000 molecules of air were CO2, and it will take mankind’s CO2 emissions 5 more years to increase that number by 1, to 40.

The “Holy Grail”: Climate Sensitivity Figuring out how much past warming is due to mankind, and how much more we can expect in the future, depends upon something called “climate sensitivity”. This is the temperature response of the Earth to a given amount of ‘radiative forcing’, of which there are two kinds: a change in either the amount of sunlight absorbed by the Earth, or in the infrared energy the Earth emits to outer space.

The ‘consensus’ of opinion is that the Earth’s climate sensitivity is quite high, and so warming of about 0.25 deg. C to 0.5 deg. C (about 0.5 deg. F to 0.9 deg. F) every 10 years can be expected for as long as mankind continues to use fossil fuels as our primary source of energy. NASA’s James Hansen claims that climate sensitivity is very high, and that we have already put too much extra CO2 in the atmosphere. Presumably this is why he and Al Gore are campaigning for a moratorium on the construction of any more coal-fired power plants in the U.S.

You would think that we’d know the Earth’s ‘climate sensitivity’ by now, but it has been surprisingly difficult to determine. How atmospheric processes like clouds and precipitation systems respond to warming is critical, as they are either amplifying the warming, or reducing it. This website currently concentrates on the response of clouds to warming, an issue which I am now convinced the scientific community has totally misinterpreted when they have measured natural, year-to-year fluctuations in the climate system. As a result of that confusion, they have the mistaken belief that climate sensitivity is high, when in fact the satellite evidence suggests climate sensitivity is low.

The case for natural climate change I also present an analysis of the Pacific Decadal Oscillation which shows that most climate change might well be the result of….the climate system itself! Because small, chaotic fluctuations in atmospheric and oceanic circulation systems can cause small changes in global average cloudiness, this is all that is necessary to cause climate change. You don’t need the sun, or any other ‘external’ influence (although these are also possible…but for now I’ll let others work on that). It is simply what the climate system does. This is actually quite easy for meteorologists to believe, since we understand how complex weather processes are. Your local TV meteorologist is probably a closet ‘skeptic’ regarding mankind’s influence on climate.

Climate change — it happens, with or without our help.