Posts Tagged ‘RealClimate’

RealClimate on the IPCC errors and their significance

February 15, 2010

RealClimate has a good post on the recent string of (alleged) errors in the IPCC report. It explains the IPCC proces, the nature and significance of the errors, and highlights the spin put on them by several media outlets.

Excerpt about the reported amount of land in the Netherlands that is below sea level:

Sea level in the Netherlands: The WG2 report states that “The Netherlands is an example of a country highly susceptible to both sea-level rise and river flooding because 55% of its territory is below sea level”. This sentence was provided by a Dutch government agency – the Netherlands Environmental Assessment Agency, which has now published a correction stating that the sentence should have read “55 per cent of the Netherlands is at risk of flooding; 26 per cent of the country is below sea level, and 29 per cent is susceptible to river flooding”. It surely will go down as one of the more ironic episodes in its history when the Dutch parliament last Monday derided the IPCC, in a heated debate, for printing information provided by … the Dutch government. In addition, the IPCC notes that there are several definitions of the area below sea level. The Dutch Ministry of Transport uses the figure 60% (below high water level during storms), while others use 30% (below mean sea level). Needless to say, the actual number mentioned in the report has no bearing on any IPCC conclusions and has nothing to do with climate science, and it is questionable whether it should even be counted as an IPCC error.

 And wrapping up the context of this whole manufacured controversy:

Do the above issues suggest “politicized science”, deliberate deceptions or a tendency towards alarmism on the part of IPCC? We do not think there is any factual basis for such allegations. To the contrary, large groups of (inherently cautious) scientists attempting to reach a consensus in a societally important collaborative document is a prescription for reaching generally “conservative” conclusions. And indeed, before the recent media flash broke out, the real discussion amongst experts was about the AR4 having underestimated, not exaggerated, certain aspects of climate change. These include such important topics as sea level rise and sea ice decline (see the sea ice and sea level chapters of the Copenhagen Diagnosis), where the data show that things are changing faster than the IPCC expected.


Guest post at Realclimate on aerosol nucleation and climate

April 24, 2009

Guess it’s a little late notice, but I have a guest post at RealClimate on the potential effects of aerosol nucleation and cosmic rays on climate. For the whole article please see RealClimate. The bottom line is as follows.


Freshly nucleated particles have to grow by about a factor of 100,000 in mass before they can effectively scatter solar radiation or be activated into a cloud droplet (and thus affect climate). They have about 1-2 weeks to do this (the average residence time in the atmosphere), but a large fraction will be scavenged by bigger particles beforehand. What fraction of nucleated particles survives to then interact with the radiative budget depends on many factors, notably the amount of condensable vapor (leading to growth of the new particles) and the amount of pre-existing particles (acting as a sink for the vapor as well as for the small particles). Model-based estimates of the effect of boundary layer nucleation on the concentration of cloud condensation nuclei (CCN) range between 3 and 20%. However, our knowledge of nucleation rates is still severely limited, which hampers an accurate assessment of its potential climate effects. Likewise, the potential effects of galactic cosmic rays (GCR) can only be very crudely estimated. A recent study found that a change in GCR intensity, as is typically observed over an 11 year solar cycle, could, at maximum, cause a change of 0.1% in the number of CCN. This is likely to be far too small to make noticeable changes in cloud properties.

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