In the Northern Hemisphere, the late 20th / early 21st century has been the hottest time period in the last 400 years at very high confidence, and likely in the last 1000 – 2000 years (or more). It has been unclear whether this is also true in the Southern Hemisphere. Three studies out this week shed considerable new light on this question. This post provides just brief summaries; we’ll have more to say about these studies in the coming weeks. More »
Technical Note: We have changed the contact email for the blog to reduce the amount of unsolicited email. If you want to contact us at the blog, please use contact-at-realclimate.org.
HadCRUT4 data now available
Just a quick note to point out that the HadCRUT4 data are now fully available for download. Feel free to discuss (or point to) any analyses you’d like to see done in the comments, and perhaps we’ll update this post with the more interesting ones.
Evaluating a 1981 temperature projection
Guest commentary from Geert Jan van Oldenborgh and Rein Haarsma, KNMI
Sometimes it helps to take a step back from the everyday pressures of research (falling ill helps). It was in this way we stumbled across Hansen et al (1981) (pdf). In 1981 the first author of this post was in his first year at university and the other just entered the KNMI after finishing his masters. Global warming was not yet an issue at the KNMI where the focus was much more on climate variability, which explains why the article of Hansen et al. was unnoticed at that time by the second author. It turns out to be a very interesting read.
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References
- J. Hansen, D. Johnson, A. Lacis, S. Lebedeff, P. Lee, D. Rind, and G. Russell, "Climate Impact of Increasing Atmospheric Carbon Dioxide", Science, vol. 213, pp. 957-966, 1981. http://dx.doi.org/10.1126/science.213.4511.957
Data presentation: A trend lesson
I just came across an interesting way to eliminate the impression of a global warming. A trick used to argue that the global warming had stopped, and the simple recipe is as follows:
Updating the CRU and HadCRUT temperature data
The latest incarnation of the CRUTEM land surface temperatures and the HadCRUT global temperatures are out this week. This is the 4th version of these products, which have undergone a number of significant changes over that time and so this is a good opportunity to discuss how and why data products evolve and what that means in the bigger scheme of things.
