Coverage bias in the HadCRUT4 temperature record

Kevin Cowtan and Robert Way


The Met Office temperature record, HadCRUT4, is widely quoted as a measure of global warming. However observations are only available for about 84% (five sixths) of the planet. The omitted region includes the Arctic, which is warming much faster than the rest of the planet. As a result, HadCRUT4 underestimates the rate of warming in recent years.

We have developed a method for using satellite data to fill in the gaps in the Met Office data. Our global record suggests that surface temperatures have been warming two and a half times faster than Met Office estimates over the past 16 years. Temperature trends starting in 1997 or 1998 are particularly affected.

This web site provides material relating to the paper "Coverage bias in the HadCRUT4 temperature record", published in Quarterly Journal of the Royal Meteorological Society.

For more details and background information, see the Briefing document.

If you would like to watch videos about the paper or get media materials relating to the project, follow the Media link.

If you would like to obtain global coverage temperature series running from various start dates to the present, follow the Temperature series link.

If you would like to access the data and methods from the paper, follow the Methods and data link.