Thursday, September 24, 2009

latest climate data

Many people want to disregard the politics surrounding climate change and AGW. Despite comments about ideology and politicization of science, there are those who still want the whole mess to be just reduced to the facts: what do the data indicate?

Here is a site that presents the data, in historical context, in as neutral, objective a fashion as I have seen.

A recent example is this pdf which contains graphs of temperature, temperature change and CO2 from each of the four sources of temperature data, such as this one:

The author offers these comments:
  • Most climate models assume the greenhouse gas carbon dioxide CO2 to influence significantly upon global temperature. Thus, it is relevant to compare the different global temperature records with measurements of atmospheric CO2, as shown in the diagrams above. Any comparison, however, should not be made on a monthly or annual basis, but for a longer time period, as other effects (oceanographic, clouds, etc.) may well override the potential influence of CO2 on short time scales such as just a few years.
  • It is of cause equally inappropriate to present new meteorological record values, whether daily, monthly or annual, as support for the hypothesis ascribing high importance of atmospheric CO2 for global temperatures. Any such short-period meteorological record value may well be the result of other phenomena than atmospheric CO2.
  • What exactly defines the critical length of a relevant time period to consider for evaluating the alleged high importance of CO2 remains elusive, and is still a topic for debate. The critical period length must, however, be inversely proportional to the importance of CO2 on the global temperature, including feedback effects, such as assumed by most climate models.
  • After about 10 years of global temperature increase following global cooling 1940-1978, IPCC was established in 1988. Presumably, several scientists interested in climate then felt intuitively that their empirical and theoretical understanding of climate dynamics was sufficient to conclude about the importance of CO2 for global temperature. However, for obtaining public and political support for the CO2-hypothesis the 10 year warming period leading up to 1988 in all likelihood was important. Had the global temperature instead been decreasing, public support for the hypothesis would have been difficult to obtain. Adopting this approach as to critical time length, the varying relation (positive or negative) between global temperature and atmospheric CO2 has been indicated in the lower panels of the three diagrams above.
So the data show 40 years of cooling, followed by a 20 year period of temperature increase, followed by the present period of another 10 years of cooling.

In the midst of the warming phase the dogma for AGW was established and has been developed as the central platform for ideological environmentalism since then.

Science gives us measurement. Meaning is provided by us.

And what meaning is applied to those measurements varies with ideology, politics, values and agendas of those framing the public policy issues that arise from the meaning they apply to those data. The data may be neutral: the meaning they are given is never neutral nor free of ideology.

Data do not change your perspective. Your perspective changes your data.