Human Carbon Dioxide Emissions Reverse 2000 Years of Arctic Cooling

[Skyhunter]

http://www.ucar.edu/news/releases/2009/arctic2k.jsp

Arctic temperatures in the 1990s reached their warmest level of any decade in at least 2,000 years, new research indicates. The study, which incorporates geologic records and computer simulations, provides new evidence that the Arctic would be cooling if not for greenhouse gas emissions that are overpowering natural climate patterns.

The associated albedo flip will amplify the warming.

 

[dorlomin]

One of the arguments against AGW causing problems is that the spectra where CO2 absorbs IR is saturated by water absorbing. This is not a problem with the arctic atmosphere. Its too dry.

This is not the only source of Arctic amplificaiton but it is one of them.

 

[Xnn]

The new study is the first to quantify a pervasive cooling across the Arctic on a decade-by-decade basis that is related to an approximately 21,000-year cyclical wobble in Earth's tilt relative to the Sun. Over the last 7,000 years, the timing of Earth's closest pass by the Sun has shifted from September to January. This has gradually reduced the intensity of sunlight reaching the Arctic in summertime, when Earth is farther from the Sun.

The research team's temperature analysis shows that summer temperatures in the Arctic, in step with the reduced energy from the Sun, cooled at an average rate of about 0.2 degrees Celsius (about .36 degrees Fahrenheit) per thousand years. The temperatures eventually bottomed out during the "Little Ice Age," a period of widespread cooling that lasted roughly from the 16th to the mid-19th centuries.

Even though the orbital cycle that produced the cooling continued, it was overwhelmed in the 20th century by human-induced warming. The result was summer temperatures in the Arctic by the year 2000 that were about 1.4 degrees C (2.5 degrees F) higher than would have been expected from the continued cyclical cooling alone.

"If it hadn't been for the increase in human-produced greenhouse gases, summer temperatures in the Arctic should have cooled gradually over the last century," says Bette Otto-Bliesner, an NCAR scientist who participated in the study.

So, while "Global Warming" did not offically start until about 1950, "Artic Warming" started far sooner.

Could we call it around 1900?

 

[Skyhunter]

One of the arguments against AGW causing problems is that the spectra where CO2 absorbs IR is saturated by water absorbing. This is not a problem with the arctic atmosphere. Its too dry.

This is not the only source of Arctic amplificaiton but it is one of them.

CO₂ does not have an instantaneous effect. The reason CO₂ has an effect on climate is due to the fact that it is a long lived greenhouse gas.

 

[Xnn]

Currently the ongoing increase of CO2 in the atmosphere is contributing about 0.015C/year to average annual global temperatures. This value is so small that it is hardly noticeable.

El Nino an La Nina on the other hand can swing global temperatures about 0.3C within a year or two. So, while CO2 additions do have a long term impact, it can be easily overwhelmed in the short term. It takes about 20 years of CO2 addition (at current rates) to approximately equal the amount of temperature swing we see from El Nino/La Nina (0.3/0.015).