Roy Spencer: 'I examined all of the major hurricane (Cat 3+) strikes in Texas since 1870 and plotted them as red dots on the time series of sea surface temperature variations over the western Gulf of Mexico. As can be seen, major hurricanes don’t really care whether the Gulf is above average or below average in temperature:'
'Michael Mann’s claim in The Guardian that it’s due to the jet stream being pushed farther north from global warming makes me think he doesn’t actually follow weather like those of us who have actual schooling in meteorology (my degree is a Ph.D. in Meteorology). We didn’t have a warm August in the U.S. pushing the jet stream farther north.'
'We already know that major landfalling hurricanes in the U.S. have been less frequent in recent decades. But once one forms, if it stalls near the coast (a rarity), it can be expected to cause a flooding disaster…especially in a flood-prone area like Houston.'
Mann: "Harvey was almost certainly more intense than it would have been in the absence of human-caused warming, which means stronger winds, more wind damage and a larger storm surge...In conclusion, while we cannot say climate change “caused” Hurricane Harvey (that is an ill-posed question), we can say is that it exacerbated several characteristics of the storm in a way that greatly increased the risk of damage and loss of life. Climate change worsened the impact of Hurricane Harvey."
'Temperatures recorded in the 20th century may not be unprecedented in the last 2000 years, as reconstruction showed records for the period from 981 to 1100, and again from 1201 to 1270, were comparable to those of the present warm period'
New technical paper in GeoResJ: "After applying the latest big data technique to six 2,000 year-long proxy-temperature series we cannot confirm that recent warming is anything but natural – what might have occurred anyway, even if there was no industrial revolution.There are, however, multiple lines of evidence indicating it was about a degree warmer across Europe during the MWP – corresponding with the 1200 AD rise in our Northern Hemisphere composite. In fact, there are oodles of published technical papers based on proxy records that provide a relatively warm temperature profile for this period. This was before the Little Ice Age when it was too cold to inhabit Greenland.
“Frankly, this study does indicate that it may be more of an uphill battle than we previously thought in order to stabilize warming below the commonly defined dangerous limit of 2 degrees Celsius,” said Pennsylvania State University’s Michael Mann, one of the study’s authors.