Low confidence in trend and attribution of droughts and hurricanes, doh!

In climate change communication droughts and hurricanes are two constants. We hear there is an increase in droughts, of course due to global warming. Also, more hurricanes are the fingerprint of a warming world. It looks strange because nor droughts nor hurricanes are on the increase, but it has been told so many time that a lot of people believe it.

Therefor it was a surprise to see the extreme weather table in SPM AR5 (table SPM.1 on page 23) and even more when comparing it with the similar table in SPM AR4 (table SPM.2 on page 8).

This is the comparison table:

  Likelihood of future trends
Phenomenon and direction of trend Likelihood that trend occurred in late 20th century (typically post-1960) Likelihood of a human contribution to observed trend Early 21st century Late 21st century
  AR4 → AR5 AR4 → AR5 AR4 → AR5 AR4 → AR5
Area affected by droughts increases Likely in many regions since 1970 → Low confidence on global scale/Likely changes in some regions More likely than not → Low confidence Likely → Low confidence Likely → Likely (medium confidence ) on a regional to global scale
Intense tropical cyclone activity increases Likely in many regions since 1970 → Low confidence in long term (centennial) changes. Virtually certain in North Atlantic since 1970 More likely than not → Low confidence Likely → Low confidence Likely → More likely than not in the Western North Pacific and North Atlantic
Droughts

Likelihood of the trend occurred since late 20th century went from “likely in many regions since 1970” to “Low confidence on global scale/likely changes in some regions”. Rather odd that they had to adjust their assessment for a trend that supposedly was there, “clear” to see. Some areas were likely to change, but globally there is not much confidence.

The same with human attribution: this went from “More likely” in AR4 to “Low confidence” in AR5. Nice to hear.

Likelihood of future trend went from “Likely” to “Low confidence” in the early 21th century and “Likely” on a regional to global scale. After hearing so many horror stories about droughts this seems serious backpedaling.

Tropical cyclone activity

Like droughts the trend occurred since the late 20th century went from “likely in many regions since 1970” to “Low confidence on a global scale”, but “Virtually certain in North Atlantic”.

The likelihood of human attribution went from “More likely than not” in AR4 to “Low confidence” in AR5.

Also the future likelihood short term went from “Likely” to “Low confidence” and on long term the confidence is assigned to “More likely than not”. Not that much confidence anymore.

Well, low confidence of human attribution and short term increases in droughts and hurricanes. That’s good news! Until now we were bombarded with loads of doom stories. Now those seems to to be based on nothing much. Pity this was not in the press release. Wouldn’t it be great when the public got to know such things? 😉

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