Marcel Crok

Clintel Foundation

Prior to the mid‐19th century, Earth was in the grip of the Little Ice Age. Since then, temperatures have on average trended upward. At the same time, human emissions of carbon dioxide (CO 2 ) have increased, and the interest of scientists has turned to consider the extent of the relative contributions of anthropogenic CO 2 and natural forces to wa...

The IPCC in its 6th Assessment report (AR6) ignored crucial peer-reviewed literature showing that normalised disaster losses have decreased since 1990 and that human mortality due to extreme weather has decreased by more than 95% since 1920. The IPCC, by cherry picking from the literature, drew the opposite conclusions, claiming increases in damag...

A statistical analysis was applied to Northern Hemisphere land surface temperatures (1850–2018) to try to identify the main drivers of the observed warming since the mid-19th century. Two different temperature estimates were considered—a rural and urban blend (that matches almost exactly with most current estimates) and a rural-only estimate. The r...

The widely used Global Historical Climatology Network (GHCN) monthly temperature dataset is available in two formats - non-homogenized and homogenized. Since 2011, this homogenized dataset has been updated almost daily by applying the "Pairwise Homogenization Algorithm" (PHA) to the non-homogenized datasets. Previous studies found that the PHA can...

The widely used Global Historical Climatology Network (GHCN) monthly temperature dataset is available in two formats—non-homogenized and homogenized. Since 2011, this homogenized dataset has been updated almost daily by applying the “Pairwise Homogenization Algorithm” (PHA) to the non-homogenized datasets. Previous studies found that the PHA can pe...

In 2016, the Royal Dutch Meteorological Office (KNMI) homogenized the daily temperature records for the Netherlands from 1901 to 1950 to allow a realistic comparison of the temperatures from 1901 to the present. The homogenizations for the main station De Bilt were carried out using a Percentile Matching Method (PMM) with one reference station and...

This report (written in Dutch) discusses the KNMI climate scenarios for The Netherlands. We give arguments why these scenarios will likely not come true. We also explain that most of the warming so far in The Netherlands is due to a jump in the temperature at the end of the 1980-ies.

In the Netherlands, there is a vigorous debate on ammonia emissions, atmospheric concentrations and deposition between stakeholders and research institutions. In this article, we scrutinise some aspects of the ammonia discourse. In particular, we want to improve the understanding of the methodology for handling experimentally determined ammonia emi...

De focus van onderliggend onderzoek ligt op ammoniakemissies bij bemesting en op trends in atmosfeer- concentraties. Daartoe hebben we van de Wageningen University & Research (WUR) enkele meetreeksen van bemestingsproeven ontvangen (overigens zonder vermelding van spreiding van meetdata en meetonzekerheid) tezamen met het rekenmodel om die metingen...

The Climate Dialogue weblog has been a climate change communication project, following a request by the Dutch Parliament, which asked the Dutch Government ‘to also involve climate sceptics in future studies on climate change’. Climate Dialogue was set up by the Royal Netherlands Meteorological Institute (KNMI), the Netherlands Environmental Assessm...

This report shows that the best observational evidence indicates our climate is considerably less sensitive to greenhouse gases than climate models are estimating. The clues for this and the relevant scientific papers are all referred to in the recently published Fifth Assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC)....

We investigate the spatial extent of a statistically highly significant shift in atmospheric temperatures over Europe around 1987-1988 using a boot-strap change point algorithm. According to this algorithm, this change point (average warming of about one degree Celsius) is statistically highly significant (p > 99.9999%). The change point is consist...

Evidence that earth's atmosphere has been warming during the last decades is unequivocal and is attributed to the gradual increase in greenhouse gases, in particular carbon dioxide (CO2). However, the notion of a "global" and "gradual" warming is to some extent misleading: changes can occur rapidly, and there are regions that have been warming fast...