Open Mind

Summary for Voters

February 2nd, 2007 · 5 Comments

The Intergovernmental Panel on Climate Change (IPCC) has released the Summary for Policymakers, part of the report of working group 1 on the physical science of climate change, which is part of the larger “fourth assessment report,” or FAR. The FAR, to be released in stages throughout 2007, supercedes the TAR, or third assessment report, issued in 2001.

Since you, the voters, are policymakers, I thought it would be useful to mention a few points from the report. Those who are deeply interested can download the preliminary version from the website of the IPCC.

Here’s the most “potent” statement in the summary:

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.

The word “unequivocal” was carefully chosen. There’s no doubt, earth’s climate is getting hotter. The evidences listed include, but are not limited to,

• Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850). The updated 100-year linear trend (1906–2005) of 0.74 [0.56 to 0.92]°C is therefore larger than the corresponding trend for 1901-2000 given in the TAR of 0.6 [0.4 to 0.8]°C. The linear warming trend over the last 50 years (0.13 [0.10 to 0.16]°C per decade) is nearly twice that for the last 100 years. The total temperature increase from 1850 – 1899 to 2001 – 2005 is 0.76 [0.57 to 0.95]°C. Urban heat island effects are real but local, and have a negligible influence (less than 0.006°C per decade over land and zero over the oceans) on these values.

• New analyses of balloon-borne and satellite measurements of lower- and mid-tropospheric temperature show warming rates that are similar to those of the surface temperature record and are consistent within their respective uncertainties, largely reconciling a discrepancy noted in the TAR.

• Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system. Such warming causes seawater to expand, contributing to sea level rise.

Given all the available evidence of what earth’s average temperature is now, and was in the past, the summary concludes:

Paleoclimate information supports the interpretation that the warmth of the last half century is unusual in at least the previous 1300 years. The last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to 4 to 6 metres of sea level rise.

And what is the cause of the increased temperature of the globe?

Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.

What will the near future bring?

For the next two decades a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected.

I’m sure denialists will claim that IPCC is stating that nothing we do will make any difference. Nothing could be further from the truth. Indeed more warming and sea level rise are “in the pipeline,” even if we could halt emissions today. So, things are going to get worse. But how much worse depends on what we do today. If we continue with cavalier emissions, the future will be a lot worse than if we accept the sacrifices today. An ounce of prevention is worth a gigaton of cure.

One of the dangers is that as earth warms, the systems that absorb CO2 from the air (the soil and the oceans) tend to take up less. This leads to a “carbon cycle feedback,” which threatens to send atmospheric CO2 levels even higher than expected:

• Warming tends to reduce land and ocean uptake of atmospheric carbon dioxide, increasing the fraction of anthropogenic emissions that remains in the atmosphere. For the A2 scenario, for example, the climate-carbon cycle feedback increases the corresponding global average warming at 2100 by more than 1°C. Assessed upper ranges for temperature projections are larger than in the TAR (see Table SPM-2) mainly because the broader range of models now available suggests stronger climate-carbon cyclefeed backs.

All in all, the fourth assessment report (FAR) is not a rosy picture of the future. But we still have time to act in such a way that the damage done to the planet, and the suffering of the next generation, are bearable. Future generations will either bless our wisdom and sacrifice, or curse our folly; the choice is up to us. But we can no longer afford to wait. The cost of delay is vastly greater than the burden of sacrifice.

Tags: Global Warming

5 responses so far ↓

  • timethief // Feb 3rd 2007 at 6:11 am

    We must act. Each and every one of us must begin to make all the changes they can as fast as they can to reduce greenhouse gas emissions. act. My fear is that we will burn ourselves out while flailing about remonstrating and “discussing” what to do. We must act now in our homes, schools, at work and in all places.

  • timethief // Feb 3rd 2007 at 6:14 am

    I’m cringing because I used the word “they” above as though I wasn’t including myself. The truth is that I live a very simple, modest and extremely frugal lifestyle. I will have very few adjustments to make to become “carbon neutral”.

  • britandgrit // Feb 3rd 2007 at 6:40 am

    Hi Tamino

    I have looked at the IPCC site but could not find the preliminary version. Can you tell me what it is listed as please.


    the Brit

  • tamino // Feb 3rd 2007 at 12:33 pm

    You can get it by going to ipcc and clicking the “download summary for policymakers” link, or just click here. Enjoy!

  • Mark Hadfield // Feb 6th 2007 at 8:51 am

    Please use the official acronym, AR4. It’s more meaningful and otherwise, what are you going to when no. 5 comes out?

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