KNMI: The state of the climate

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The 5 yearly report “The state of the Climate” (in Dutch only) has just been released by the KNMI (Royal Dutch Meteorological Institute). It’s focused on the Dutch climate, but put in a global perspective, and it’s aimed at governments, organizations, and the general public. A main conclusion is that The Netherlands has warmed up more than twice as fast as the global average.

 

That’s in principle not so surprising, because land warms up faster than oceans. The extra warmth is being mixed (and thus tampered) in the upper water column, and water has a large heat capacity (which causes it to warm up less with the same input of energy). Indeed, most of Europe has warmed faster than the global average. The Netherlands also has also gotten more precipitation during the past 100 years.

 

Dutch and global temperature (anomaly) trends 1950-2008

Dutch and global temperature (anomaly) trends 1950-2008

 

Figure 2.1 from the report shows that the temperature in The Netherlands fluctuates much more than the global temperature. That makes perfect sense, because random variations are averaged out to a greater extent when more measurements are included. That is valid for more measurements in space (global versus Dutch) and e.g. also for more measurements in time (40 versus 5 years).  Logical as this may be, you would be surprised how often anthropogenic climate change is being denied, based on 5 (sometimes even 1) year temperature trends, or based on that one glacier in Africa (or was it the Himalaya?) that has increased in length. You can easily find these kinds of arguments on the internet and certain other media (but you won’t hear them at a scientific conference). That has the positive side effect that it can act as a warning signal that the information on such a website is not scientifically sound (even though they often try very hard to make it appear scientific).

 

The discussion about the temperature trends ends with the statement that “a connection with the enhanced greenhouse effect seems logical, but hasn’t been shown/proven yet” (my translation). Such a sentence seems more geared towards scientists than the general audience, which is the stated target group of the report. I think that the uncertainty here is mainly a consequence of the large variability of the temperature signal over a small area (as discussed above), and that makes it difficult to draw hard conclusions from it (in comparison to global temperature trends). And of course, there is no strict proof in the mathematical sense (nor will there ever be).

 

Most readers of the report will interpret this very differently however. Many will interpret it as meaning that it’s quite possible that the (local or global?) temperature rise has nothing to do with rising greenhouse gases. However, the chance of that being the case is very small indeed. Uncertainty has a very different meaning in the scientific jargon than in daily language. Oftentimes, science communication fails to convey a proper understanding of the relative (un)certainty, which is a shame.

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