Skeptical Science - Details

The2009 State of the Climate reportof the US National Oceanic and Atmospheric Administration (NOAA), released in mid-2010, brings together many different series of data “from the top of the atmosphere to the depths of the ocean”. The conclusion? All of these independent lines of evidence tell us unequivocally that the Earth is warming.

The very accessible10-page summaryexamines the trends for 10 key climate indicators using a total of 47 different sets of data. All of the indicators expected to increase in a warming world, are in fact increasing, and all that are expected to decrease, are decreasing:

The 10 indicators are:

1. Land surface air temperatureas measured by weather stations. You know all those skeptic arguments about how the temperature record is biased by the urban heat island effect, badly-sited weather stations, dropped stations, and so on? This is the only indicator which suffers from all those problems. So if you’re arguing with somebody who tries to frame the discussion as being about land surface air temperature, just remind them about the other nine indicators.
2. Sea surface temperature. As with land temperatures, the longest record goes back to 1850 and the last decade is warmest.
3. Air temperature over the oceans.
4. Lower troposphere temperatureas measured by satellites for around 50 years. By any of these measures, the 2000s was the warmest decade and each of the last three decades has been much warmer than the previous one.
5. Ocean heat content, for which records go back over half a century. More than 90% of the extra heat from global warming is going into the oceans – contributing to a rise in…
6. Sea level. Tide gauge records go back to 1870, and sea level has risen at an accelerating rate.
7. Specific humidity, which has risen in tandem with temperatures.
8. Glaciers. 2009 was the 19th consecutive year in which there was a net loss of ice from glaciers worldwide.
9. Northern Hemisphere snow cover, which has also decreased in recent decades.
10. Perhaps the most dramatic change of all has been inArctic sea ice. Satellite measurements are available back to 1979 and reliable shipping records back to 1953. September sea ice extent has shrunk by 35% since 1979.

Science isn’t like a house of cards, in that removing one line of evidence (eg. land surface air temperature) wouldn’t cause the whole edifice of anthropogenic global warming to collapse. Rather, “land surface warming” is one of more than ten bricks supporting “global warming”; and with global warming established, there isa whole other set of brickssupporting “anthropogenic global warming”. To undermine these conclusions, you’d need to remove most or all of the bricks supporting them – but as the evidence continues to pile up, that is becoming less and less likely.

This post is theBasic version(written by James Wight) of the skeptic argument "It's not happening".

A Scientific Guide to the 'Skeptics Handbook'is now available inSpanishandCatalan. Many thanks to Ferran Vilar who translated both. He also helped translate many of theskeptic rebuttals into Spanish(alongside the prolific Jesús Rosino). You can check out more of Ferran's work at his blogustednoselocree.com.

Spanish

Catalan

The handbook has also been translated into a few other languages, shown below. If you're interested in helping translate the Guide into another language, you candownload the Word document, translate it and email me the translation. I'll then insert the translated text into the existing design and email back a PDF to check that it all came out right. But best first tocontact meto ensure noone else is already working on your language.

Czech

German

Italian

Skeptics often claim that the science of anthropogenic global warming (AGW) is not “settled”. But to the extent that this statement is true it is trivial, and to the extent that it is important it is false. No science is ever “settled”; science deals in probabilities, not certainties. When the probability of something approaches 100%, then we can regard the science, colloquially, as “settled”.

The skeptics say that results must be double-checked and uncertainties must be narrowed before any action should be taken. This sounds reasonable enough – but by the time scientific results are offered up to policymakers, they have already been checked and double-checked and quintuple-checked.

Scientists have been predicting AGW, with increasing confidence, for decades (indeed, the idea was first proposed in 1896). By the 1970s, the scientific community were becoming concerned that human activity was changing the climate, but were divided on whether this would cause a net warming or cooling. As science learned more about the climate system, a consensus gradually emerged. Many different lines of inquiry all converged on the IPCC’s 2007 conclusion that it is more than 90% certain that anthropogenic greenhouse gases are causing most of the observed global warming.

Some aspects of the science of AGW are known with near 100% certainty. The greenhouse effect itself is as established a phenomenon as any: it was discovered in the 1820s and the basic physics was essentially understood by the 1950s. There is no reasonable doubt thatthe global climate is warming. And there is alsoa clear trail of evidenceleading to the conclusion that it’s caused by our greenhouse gas emissions. Some aspects are less certain; for example, the net effect of aerosol pollution is known to be negative, but the exact value needs to be better constrained.

What about the remaining uncertainties? Shouldn’t we wait for 100% certainty before taking action? Outside of logic and mathematics, we do not live in a world of certainties. Science comes to tentative conclusions based on the balance of evidence. The more independent lines of evidence are found to support a scientific theory, the closer it is likely to be to the truth. Just because some details are still not well understood should not cast into doubt our understanding of the big picture: humans are causing global warming.

In most aspects of our lives, we think it rational to make decisions based on incomplete information. We will take out insurance when there is even a slight probability that we will need it. Why should our planet’s climate be any different?

This post is theBasic version(written by James Wight) of the skeptic argument "The science isn't settled".