Article: GLOBE WARMING TOWARD TWO DEGREES CELSIUS: THE EU'S UPPER LIMIT

GLOBE WARMING TOWARD TWO DEGREES CELSIUS: THE EU'S UPPER LIMIT

Andrew Glikson
Earth and paleoclimate scientist
Australian National University

Taking into account the (1) masking effect of industry-emitted sulphur aerosols, and (2) lost reflectance (albedo) due to Arctic Sea ice melt and other parts of the polar and mountain glaciers, global temperature-equivalents are tracking close to the European Union maximum permissible level of 2 degrees Celsius.

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According to the IPCC AR4-2007 report [1] a total anthropogenic greenhouse factor of 3.06 Watt/m2, equivalent to about +2.3 degrees C, is masked by a compensating aerosol albedo effect of -1.25 Watt/m2 (mainly sulphur from industrial emissions) equivalent to about -0.9C (without land clearing albedo gain and ice melt albedo loss) (Table 1). Once the short-lived aerosols dissipate, adding the reflectance loss of melting polar ice (where maximum warming of up to 4 degrees C occurs, mean global temperatures track toward +2 degrees C, considered by the European Union to be the maximum permissible level.

From Table 1, subtracting the aerosol masking effect, the magnitude of the 1750 -- 2005 mean forcing at ~3 Watt/m2 is approaching 50% of the total last glaciation termination of 6.5+/-1.5 Watt, not accounting for developments since 2005. This includes the reduction in albedo due to melting of Arctic Sea ice and other parts of the cryosphere.Since the mid-1990s the mean global temperature trend has become increasingly irregular, representing an increase in climate variability with global warming, as reflected by variations in the ENSO cycle and oscillating ice melt and re-freeze cycles.

The solar sunspot cycle effect is at about +/-0.1 degrees C, an order of magnitude less than greenhouse forcing. Sharp peaks include the 1998 El-Nino peak (near +0.55C) and the 2007 La Nina trough (near -0.7C) [2]. Mean global temperature continued to rise during 1999-2005 by about 0.2C.The effects of this warming on the cryosphere include:

(A) Reduction in the Arctic Sea multi-year ice cover from about 4.2 to 2.5 million square km during 2000-2009 [3].

(B) Increase in Greenland September ice melt area from 350,000 to 550,000 square km during 1997-2007 [4].

(C) Warming of the entire Antarctic continent by 0.6C and of west Antarctic by 0.85C during 1957-2006 [5], reflected by collapse of west Antarctic ice shelves [6].

Variations in temperature and sea ice cover around Antarctica are effected by the shrinking polar wind vortex and tropospheric and stratospheric ozone layer conditions, resulting in geographic and temporal variability in sea and land ice cover(http://earthobservatory.nasa.gov/Features/WorldOfChange/sea_ice_south.php?src=eoa-ann).

Ongoing global warming may lead to the release of methane from permafrost, collapse of the North Atlantic Thermohaline current, high-energy weather events and yet little-specified shifts in atmospheric states (tipping points) [7]

Table 1. Comparisons between anthropocene (1750-2005), last glacial termination (20 -- 11.7 kyr) and Pliocene (~3 Ma) CO2 levels, climate forcings, mean global temperatures and sea levels. Sources: [1] and [19].

Period	CO2 ppm	ForcingsWatt/m²	Temperature ^oC (1^oC ~ � W/m²)	Sea levelmetres
1750 - 2005	260-387	Greenhouse: +3.06Albedo: -1.25* Current balance: +1.81Ice albedo loss (? W/m²)	~ +2.3~ -0.9?T^oC	Tracking toward Pliocene levels
Last glacial termination(20 -- 11.7 kyr	180-280	Greenhouse gases:+3.0+/-0.5 Ice sheets and vegetation albedo loss: +3.5+/-1.0.	~ +5.0+/-1.0	+120
Pliocene (3 Ma)	400		+2 to 3	+25 +/-12

*(not including land clearing)

This experiment by Homo "sapiens"- is a novel one. Developments may include periods of cooling, as may be indicated by the current slow-down of Greenland glaciers. In a recent paper by Dakos et al. (2008) abrupt climate changes in the past are shown to have been preceded by quiet periods [8].

"-Skeptics"- use such short-term variability, for example slowing down of Greenland glaciers, to argue "global cooling"- and thereby a "justification"- for further carbon emissions [9 -- 11].

The implications of climate change for ecosystems are illustrated in the new book "Heatstroke: Nature in an Age of Global Warming"- by Anthony Barnosky, of Yale University, who states: "I think probably the biggest cause for worry is we really are seeing the disappearance of whole ecological niches, which means extinctions." [12].

Despite intensified warnings from the Copenhagen climate conference [13], as a self-fulfilling prophecy the "great moral issue of our time"- [14] is being relegated to secondary priority [15].

Given that warnings by scientists have proven mostly correct, as contrasted with watered-down reports percolating upward through bureaucracies, there is little evidence the authorities are listening to the recent dire warnings by climate scientists [16].

The decline by CSIRO to report directly to the recent Senate climate inquiry [17], reminiscent of the Howard era [18], has only been saved by the courage of individual scientists, one of whom compared current targets to 'Russian roulette with the climate system with most of the chambers loaded'.

[1] http://www.ipcc.ch/ ; SPM.2.

[2] http://data.giss.nasa.gov/gistemp/graphs/Fig.C.lrg.gif

[3] http://www.nasa.gov/topics/earth/features/arctic_thinice.html

[4] http://nsidc.org/data/virtual_globes/

[5] http://www.giss.nasa.gov/research/news/20090121/

[6] http://nsidc.org/news/press/20080325_Wilkins.html

[7] http://climatechangepsychology.blogspot.com/2009/02/timothy-m-lenton-et-al-pnas-105-6.html ; http://researchpages.net/ESMG/people/tim-lenton/tipping-points/.

[8] http://www.indiana.edu/~halllab/L577/Topic3/Dakosetal_2008_PNAS.pdf

[9] http://www.worldclimatereport.com/index.php/2009/01/23/glacier-slowdown-in-greenland-how-inconvenient/

[10] http://www.connorcourt.com/catalog1/index.php?main_page=product_info&cPath=7&products_id=103 ; http://scienceblogs.com/deltoid/2009/05/ian_enting_is_checking_plimers.php http://bravenewclimate.com/2009/04/23/ian-plimer-heaven-and-earth/ ; http://www.theaustralian.news.com.au/story/0,,25433059-5003900,00.htmlhttp://www.crikey.com.au/2009/05/05/plimer-wants-to-talk-science-ok-here-goes/

[11] http://australianconservative.com/main-site/category/policy/environment/page/2/

[12] http://www.e360.yale.edu/content/feature.msp?id=2154