Wednesday, April 09, 2014

A Few More Bits from the IPCC Fifth Assessment Report

(Chapter 10, Second draft)
An assessment of the observational evidence indicates that the AR4 conclusions regarding global increasing trends in hydrological droughts since the 1970s are no longer supported. ... we conclude there is low confidence in attributing changes in drought over global land since the mid-20th century to human influence.
Contrast that to all the claims blaming the current California drought on global warming.
The average global cyclone activity is expected to change little under moderate greenhouse gas forcing

Globally, there is low confidence in any long term increases in tropical cyclone activity (Section 2.6.3) and low confidence in attributing global changes to any particular cause.
Or, in other words, Chris Landsea was right.
Anthropogenic warming remains a relatively small contributor to the overall magnitude of any individual short-term event because its magnitude is small relative to natural random weather variability on short time scales. Because of this random variability, weather events continue to occur that have been made less likely by human influence on climate, such as extreme winter cold events ...
Contrast the final sentence to occasional claims that recent unusual cold is evidence for, not against, "climate change."
The chapter also contains a graph showing estimates of northern hemisphere temperature over the past 1200 years. It appears from the green lines, due to Michael Mann of hockey stick fame, that the medieval warm period is back, with a peak close to current temperature. 


Fred Mangels said...

Just a suggestion; Maybe use italics or in some way differentiate quotes from the report from your own comments? Might make it a bit less confusing for some of us.

David Friedman said...

I've put my comments in italics. At least as seen on my machine, the quotes from the report are indented and set off by dotted colored lines, that being how quotes are formatted on blogger.

Fred Mangels said...

Ok. thanx

John Vandivier said...

Great article David! Sharing on social media and referencing on the blog now.