Federico Pistono

Vitezslav Kremlik suggests that the temperatures over the last 10 years have actually stopped increasing, and that a cooling era is about to come. While I would very much like to agree with him and experience this phenomena (we could finally focus all of our attention on other issues, such as poverty, famine, AIDS, malaria, environmental pollution, waste management, fighting criminal organisations, soil degradation, biodiversity destruction, water shortage, et cetera), but sadly, the numbers I have are very different.

According to NASA and its "Global Temperature Trends: 2008 Annual Summation" from the "GISS Surface Temperature Analysis", 2008 is the ninth warmest year in the period of instrumental measurements, which extends back to 1880 (left panel of Fig. 1) and the ten warmest years all occur within the 12-year period 1997-2008.

Figure 1. Left: Annual-means of global-mean temperature anomaly Right: Global map of surface temperature anomalies, in degrees Celsius, for 2008. (Click for PDF.)

The solar output remains low at the lowest level in the period since satellite measurements began in the late 1970s, and the time since the prior solar minimum is already 12 years, two years longer than the prior two cycles. This has led some people to speculate that we may be entering a "Maunder Minimum" situation, a period of reduced irradiance that could last for decades. Most solar physicists expect the irradiance to begin to pick up in the next several months — there are indications, from the polarity of the few recent sunspots, that the new cycle is beginning.

Figure 4. Solar irradiance through November 2008 from Frohlich and Lean. (Click for PDF.)

However, let's assume that the solar irradiance does not recover. In that case, the negative forcing, relative to the mean solar irradiance is equivalent to seven years of CO2 increase at current growth rates. So do not look for a new "Little Ice Age" in any case. Assuming that the solar irradiance begins to recover this year, as expected, there is still some effect on the likelihood of a near-term global temperature record due to the unusually prolonged solar minimum. Because of the large thermal inertia of the ocean, the surface temperature response to the 10-12 year solar cycle lags the irradiance variation by 1-2 years. Thus, relative to the mean, i.e, the hypothetical case in which the sun had a constant average irradiance, actual solar irradiance will continue to provide a negative anomaly for the next 2-3 years.

Finally, the conclusions are unequivocal: the Southern Oscillation and increasing GHGs continue to be, respectively, the dominant factors affecting interannual and decadal temperature change. Solar irradiance has a non-negligible effect on global temperature. Given our expectation of the next El Niño beginning in 2009 or 2010, it still seems likely that a new global temperature record will be set within the next 1-2 years, despite the moderate negative effect of the reduced solar irradiance.

Let us focus the attention on one particular sentence: "The Southern Oscillation and increasing GHGs continue to be, respectively, the dominant factors affecting interannual and decadal temperature change." This position and analysis is also confirmed by the 2008 report "Understanding and Responding to Climate Change".

Temperature readings from around the globe show a relatively rapid increase in surface temperature during the past century. These data, which have been
closely scrutinised and carefully calibrated to remove potential problems such as the
“urban heat island” effect, show an especially pronounced warming trend during the
past 30 years—in fact, 9 of the 10 warmest years on record have occurred during the
past decade.

Furthermore, the surface temperature data are consistent with other evidence of warming, such as increasing ocean temperatures, shrinking mountain glaciers, and decreasing polar ice cover. One inevitable question people ask is whether the current warming trend is unusual compared to temperature shifts on Earth prior to the 20th century—that is, before the build up of excess greenhouse gases in the atmosphere. To help answer this question, scientists analyse tree rings, ice cores, ocean sediments, and a number of other “proxy” indicators to estimate past climatic conditions. These studies are important for understanding many aspects of Earth’s climate, including the natural variability of surface temperature over many centuries.

Indeed, it would be nice to take a vacation and believe whatever scepticism may arise today or tomorrow. But while we are here debating something that isn't even considered among scientists worth of debating, time is running out, and people are already experiencing the disastrous effects of climate change. It is important to debate, argue and challenge each other's ideas. But there are facts that we cannot ignore, that exist regardless of what we think or believe to be true, and we should take responsibility for those facts.

I shall try to focus my attention on the more constructive activity of trying to find solutions and get people involved, with all my heart and mind.

Tck tck tck... time is running, and I have to moral obligation to answer this wake up call. I hope you will too.

Peace.

p.s. This article was crossposted on the TH!NK ABOUT IT - Climate Change blogging competition.