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Climatology Global Warming Science Topic Index

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Does atmospheric CO2 cause significant global warming?

Background

In 1896 Svante Arrhenius modeled the greenhouse effect, where gases in the atmosphere such as CO2 trap sunlight much like glass traps heat in a greenhouse. His principle is foundational in climatology, though today we have a more refined understanding of physical chemistry and we use Global Climate Models to predict that an increase in CO2 will actually result in global warming.

Implications

Is global warming caused primarily by humans?

Do negative feedback loops mostly cushion the effect of atmospheric CO2 increases?

Experts

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Agree

Experts In Science

Intergovernmental Panel on Climate Change (IPCC) Scientific Body formed by U.N.

Agree

It is very likely that glacial-interglacial CO2 variations have strongly amplified climate variations, but it is unlikely that CO2 variations have triggered the end of glacial periods. Antarctic temperature started to rise several centuries before atmospheric CO2 during past glacial terminations.

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01 Jan 2008 Source

Sub-Arguments Of This Expert:
Do negative feedback loops mostly cushion the effect of atmospheric CO2 increases?
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Svante Arrhenius Scientist, First Modeled Greenhouse Effect

Agree

A simple calculation shows that the temperature in the arctic regions would rise about 8° to 9°C., if the carbonic acid increased to 2.5 or 3 times its present value.

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01 Apr 1896 Source

Disagree

Experts In Science

Denis Rancourt Physics Professor

Mostly Disagree

CO2 increases may accompany temperature increases rather than causing them. Indeed, some high resolution studies have suggested that the temperature increases precede the CO2 increases. Interestingly, also, ice core data shows strong temporal correlations between inferred temp. and amount of dust preserved in the ice core. Finally, the older geological record shows several dramatic examples of where CO2 concentration and global average temperature were either unrelated or even anti-correlated.

The Cause vs Correlation Pitch The Ignored Evidence Pitch

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27 Feb 2007 Source

Syun-Ichi Akasofu Geophysics Professor

Disagree

If you look back far enough, we have a bunch of data that show that warming has gone on from the 1600s with an almost linear increase to the present.

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01 Apr 2007 Source

Gerhard Gerlich Physics Professor

Disagree

There is no atmospheric greenhouse effect, in particular CO2-greenhouse effect, in theoretical physics and engineering thermodynamics. Thus it is illegitimate to deduce predictions which provide a consulting solution for economics and intergovernmental policy.

The Ignored Evidence Pitch

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07 Jul 2007 Source

Comments

Collective

Agree

Many gases in our atmosphere have a greenhouse effect. If it wasn't for these gases, Earth's atmosphere would be much cooler.

There is a real scientific debate concerned with the feedback effects of additional greenhouse gases in the atmosphere. However, some skeptics are actually claiming that CO2 has no greenhouse effect at all.

Denis Rancourt, who is not even a climatologist, is very misleading when he says: "CO2 increases may accompany temperature increases rather than causing them. Indeed, some high resolution studies have suggested that the temperature increases precede the CO2 increases." He makes it sound as if new studies have recently revealed this information. In fact, climatologists have been aware for 20 years of the fact that in Earth's history, CO2 has lagged temperature. New studies have only confirmed what they already had good evidence for. He makes it sound as if the new studies are actually refuting fundamental assumptions of climatologists.

When the Earth was coming out of previous glacial periods, it was changes in Earth's orbit that began the warming. As the Earth slowly warmed, various feedback effects, such as the warmer ocean's decreased ability to absorb CO2, caused an increase in CO2 levels. These greenhouse gases in turn further *amplified* the warming (this is called a positive feedback loop, which is a basic concept in climatology).

Today's climate is unique in that it's actually the CO2 (and other greenhouse gases) that are initiating the warming. So the skeptics are way off the mark when they make direct comparisons with the past without taking into account the complexity of the climate system. This is especially ironic, given that it's the skeptics who make out that it's the IPCC who are oversimplifying climate.

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Individual

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DGwartney gave their takeonit on 08 May 2009

Agree

Positive and negative feedbacks on the climate are basically used to define the stability of a given climate. Positive feedbacks are those that directly impact the earth’s climate system which can cause a change in climate to occur, leading to even further change in the climate. A negative feedback is one that may cause a climate change, but effectively leads to further mechanisms that act as mitigation towards negative impacts that can emerge from environmental change.

A very strong example of a positive feedback mechanism is ocean warming. This is a very important topic that many researchers have been studying for quite some time. This is a positive feedback due to the ability of water to act as a sink for CO2. The oceans are great sources for absorbing CO2 from the atmosphere which is beneficial to cooling the atmosphere. However, as air temperature increases (possibly from excess CO2 emissions) oceans will increase in temperature and will be less dense, thus losing their ability to absorb excess CO2 from the atmosphere. Due to this, increasing CO2 in the atmosphere will continue to increase air temperature, which in turn increases ocean surface temperature.

A negative feedback would be if increasing temperature leads to increasing evapotranspiration. Effectively, this would have the possibility to increase cloud cover in the atmosphere. This may be advantageous in the ability of the clouds to reflect incident solar radiation, thus leading to cooler temperatures. There is a caveat to this though; if the increase in clouds are low they will indeed cool, but if the clouds produced act as cirrus (very high) they would have the ability to increase temperature. This falls in the category of possibly increasing the greenhouse effect with increasing cirrus formation.

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