Global Warming Science - www.appinsys.com/GlobalWarming

Arctic Cycles – Related to AMO Not CO2

[last update: 2009/09/25]

The following graph shows the average temperature anomaly for the Arctic from the Hadley CRUTEM3 database (www.cru.uea.ac.uk/cru/data/temperature/). This graph is the average of all 5x5 degree cells north of 60 degrees N, having data starting prior to 1930 (74 grids). Overlain shapes indicate periods of relative stasis (blue rectangles) and warming (red arrows). Warming cycles started in 1920 and 1988. (Graph from HadCRU data at the AppInSys climate data visualizer.)

The following figure shows the same temperature anomaly data as above-left (blue). The years bounded by the red rectangle (1944 – 2008) have been copied, changed to red and shifted back 68 years. The pattern shows that it is a recurrent cycle and the net warming has been about 0.6 degrees between cycles.

The following figure (left) combines the HadCRU global average temperature anomalies (from: [http://hadobs.metoffice.com/hadcrut3/diagnostics/global/nh+sh/]) with the IPCC graph of model outputs (from: IPCC 2007 AR4 Figure SPM-4 [http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf]) In this figure, the blue shaded bands show the result of 19 simulations from 5 climate models using only the natural forcings. Red shaded bands show the result of 58 simulations from 14 climate models including anthropogenic CO2. This clearly shows that prior to about 1972, the global warming is fully explained by climate models using only natural forcings (i.e. no human CO2). The models need input of CO2 only after about 1970. In other words, prior to 1970 all warming was natural, according to the IPCC. The Arctic exhibits two virtually identical temperature cycles, as shown above, but the IPCC says one of them was natural and the recent one caused by CO2.

The right-hand figure below superimposes the Arctic temperatures shown above on the global average. The Arctic temperatures exhibit much greater variation than the global average.

NASA’s James Hansen (Hansen et al 2007 “Climate simulations for 1880–2003 with GISS modelE” Clim Dyn (2007) 29:661–696 [http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_3.pdf]) observed that the climate model was not correctly simulating the 1930s-1940s warm period in the global average temperature: “It may be fruitless to search for an external forcing to produce peak warmth around 1940. It is shown below that the observed maximum is due almost entirely to temporary warmth in the Arctic. Such Arctic warmth could be a natural oscillation (Johannessen et al. 2004), possibly unforced. Indeed, there are few forcings that would yield warmth largely confined to the Arctic. Candidates might be soot blown to the Arctic from industrial activity at the outset of World War II, or solar forcing of the Arctic Oscillation (Shindell et al. 1999; Tourpali et al. 2005) that is not captured by our present model. Perhaps a more likely scenario is an unforced ocean dynamical fluctuation with heat transport to the Arctic and positive feedbacks from reduced sea ice.”

So Hansen asserts that the previous warming cycle was natural (perhaps “solar forcing of the Arctic Oscillation”), but the current warming cycle is due to CO2. And yet the current “global” warming has also been “largely confined to the Arctic”.

The following figure shows the global temperature change from 1978 to 2006 for the lower troposphere from satellite data [http://climate.uah.edu/25yearbig.jpg]. Most of the warming has been in the Arctic.

The following figure is from the IPCC Fourth Assessment Report (AR4) Figure 9.6 (2007). It shows the change in temperature (C per decade) by latitude. The black line shows the observed temperature, the blue band shows the output of the computer models including only natural factors, whereas the pink band shows the output of computer models including anthropogenic CO2. Notice that the models without CO2 (blue shaded area) can explain all of the warming for most of the world up to 30 degrees north latitude. This figure also shows that the warming is mainly in the Arctic.

(See Global Warming is Not Global for more details about the non-global trends)

(See Arctic Regional Summary for more details on the Arctic)

Oceanic Oscillations

It is only in recent years that scientists are starting to recognize the influence of oceanic cycles in influencing climate. A 2008 study – “Oceanic Influences on Recent Continental Warming”, by Compo et al in Climate Dynamics, 2008) [http://www.cdc.noaa.gov/people/gilbert.p.compo/CompoSardeshmukh2007a.pdf] states: “Evidence is presented that the recent worldwide land warming has occurred largely in response to a worldwide warming of the oceans rather than as a direct response to increasing greenhouse gases (GHGs) over land. Atmospheric model simulations of the last half-century with prescribed observed ocean temperature changes, but without prescribed GHG changes, account for most of the land warming. … Several recent studies suggest that the observed SST variability may be misrepresented in the coupled models used in preparing the IPCC's Fourth Assessment Report, with substantial errors on interannual and decadal scales. There is a hint of an underestimation of simulated decadal SST variability even in the published IPCC Report.”

The Atlantic Multi-Decadal Oscillation (AMO) is a fluctuation in de-trended sea surface temperatures in the North Atlantic Ocean. It was identified in 2000 and the AMO index was defined in 2001 as the 10-year running mean of the de-trended Atlantic SST anomalies north of the equator.

The following figure shows the AMO [http://intellicast.com/Community/Content.aspx?a=127].

The following figure superimposes the Arctic average annual temperature shown at the beginning of this document on the AMO.

The following figure shows the sum of the AMO plus the Pacific Decadal Oscillation (PDO) [http://intellicast.com/Community/Content.aspx?a=127] (black line).

The following figure shows the AMO+PDO (black line above changed to red below) superimposed on the Arctic average annual temperature shown at the beginning of this document.

The above figures show the clear correlation of the Arctic temperature cycles to the oceanic oscillations.

(See Oceanic Oscillation Summary for more details on the AMO and PDO)