Roy Spencer was recently interviewed by the website Catholic Online, and unfortunately spent most of the interview repeating long-debunked climate myths. He could have simply answered the questions with factually correct information, and expressed his climate 'skepticism' where appropriate. Had he taken this approach, the Catholic Online readers could have become better informed on the subject of climate change, as well as potentially seeing where Roy Spencer's 'skepticism' comes from.
Instead, Roy Spencer responded to most of the questions with factually wrong answers. It was the sort of interview you might expect from a climate contrarian blogger like Anthony Watts, but you would hope that a climate scientist could do much, much better. Unfortunately, Spencer disappointed. Here we will compare Spencer's assertions to the body of scientific evidence and see where he went wrong.
Spencer began the interview by trying to cast doubt on the existence of global warming.
"No one knows whether it is currently warming, because we only see warming "in the rearview mirror"...after it has occurred."
To his credit, Spencer did mention that "there is some evidence that the deep ocean has continued to warm." However, we absolutely do know that the planet is currently warming. Aside from the fact that we measure that warming directly, we also know that there is a global energy imbalance due to the fact that humans have increased the greenhouse effect. Physically, we know that the planet will continue to warm as long as we continue to increase the greenhouse effect.
Spencer next repeated a variant of a myth we previously examined from his University of Alabama at Huntsville colleague, John Christy.
"It is entirely possible that summer sea ice meltback now is no worse than it was back in the 1920's and 1930's, when ship explorers reported unprecedented warming and sea ice and glacier changes in the Arctic"
While we didn't have satellites monitoring Arctic sea ice in the 1920s or 1930s or 1940s, all available data indicate that Arctic sea ice was much, much more extensive during that timeframe than today. One of the most widely used long-term estimates of Arctic sea ice extent comes from Walsh and Chapman (2001), whose data are available from the University of Illinois (updated through 2008). A description of the vast array of data used by Walsh and Chapman is available here, and the data are plotted in Figure 1.
Figure 1: Average July through September Arctic sea ice extent 1870-2008 from the University of Illinois (Walsh & Chapman 2001 updated to 2008) and observational data from NSIDC for 2009-2011 (blue), with a fourth order polynomial fit (black soiid line). Black vertical dashed lines indicate the years 1938-43.
Clearly Arctic sea ice during the early and mid-20th century was far more extensive than today. In fact, research by Kinnard et al. (2011) indicates that Arctic sea ice extent is now at its lowest in 1,450 years. There's really no point in denying this, except for denial's sake. All of the available evidence contradicts this myth.
As climate contrarians often do when asked about the Arctic sea ice death spiral, Spencer then tried to shift the focus to the Antarctic.
"Also, since 1979, sea ice around Antarctica has gradually increased, not decreased, which climate models have not been able to explain."
Eli Rabett does a great job debunking this one. In 1992, Manabe, Spellman and Stouffer predicted "the enhanced production of [Antarctic] sea ice." The paper discusses that melting ice will decrease the salinity of the ocean waters around Antarctica, which will cause decreased mixing with the relatively warmer deep ocean waters, reducing sea surface temperatures, causing more sea ice to form.
In 2002, Zwally, Comiso and Parkinson noted that the slight increase in Antarctic sea ice extent is:
"...qualitatively consistent with the counterintuitive prediction of a global atmospheric-ocean model of increasing sea ice around Antarctica with climate warming due to the stabilizing effects of increased snowfall on the Southern Ocean."
In 2010, Liu and Curry (that's climate 'skeptic' Judith Curry) arrived at the same conclusions as the Manabe and Zwally papers, but predicted that global warming will eventually catch up with Antarctic sea ice and cause it to decline over the second half of the 21st century.
It's true that some climate models predict that Antarctic sea ice should be decreasing, but as Polvani and Smith (2013) shows, the natural variability in Antarctic sea ice extent is probably larger than any trend from the forced response in models anyway. Bottom line, Antarctica is cold? Yeah, we knew that, Spencer.
Next on the 'skeptic' checklist, Spencer ticked off extreme weather event denial.
"There has been no increase in "superstorms" ... Sandy-class storms occur every year"
In fact, MIT hurricane expert Kerry Emanuel first proposed in Emanuel (1987) that warmer sea surface temperatures should lead to stronger hurricanes. Emanuel (2005) confirmed that hurricanes have grown stronger over the past several decades, in part due to human-caused global warming. As he put it in Emanuel (2012),
"In the North Atlantic region, where tropical cyclone records are longer and generally of better quality than elsewhere, power dissipation by tropical cyclones is highly correlated with sea surface temperature during hurricane season in the regions where storms typically develop"
As a result, hurricane strength and damage are projected to continue increasing in a warming world. These results are also consistent with the results of Grinsted et al. (2013), which concluded that:
"we have probably crossed the threshold where Katrina magnitude hurricane surges are more likely caused by global warming than not."
And with Holland and Bruyère (2013) which found that:
"since 1975 there has been a substantial and observable regional and global increase in the proportion of Cat 4–5 hurricanes"
Spencer expressed his skepticism about the amount of global warming that humans are causing.
"The consensus is only that humans are contributing to warming...even I would probably agree with such an innocuous statement ... Most climate researchers simply assume recent warming is manmade, but human causation is only one possible explanation out of several."
The body of scientific literature is quite clear and consistent in finding that human greenhouse gas emissions are the dominant cause of the global warming over the past 50–100 years (Figure 2).
Figure 2: Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WS12, dark green), and Jones et al. 2013 (J12, pink).
Most climate researchers don't just "assume" the warming is manmade, they defer to the body of scientific literature on the subject. And ultimately it again boils down to that fundamental physics. Humans have caused a large global energy imbalance by increasing the greenhouse effect. The planet must warm in response.
While admitting that sea levels are rising, Spencer disputed that we know the cause.
"...sea levels have indeed increased, which probably is a sign of warming ... it is difficult to attribute the current rate of rise...to humans when we don't know how much of the rise is natural."
Sea level rises for two main reasons: 1) melting land ice, and 2) thermal expansion. Both of those contributors are results of global warming. If humans are causing global warming (and as just discussed, we are), then we're causing sea level to rise.
Spencer next claimed that "there is very little research into" natural causes of climate change. That is simply untrue. For example, the Intergovernmental Panel on Climate Change (IPCC) has a thorough summary of research on natural climate change causes in its reports, including in its Summary for Policymakers. Studies which attempt to determine the causes of global warming also investigate natural causes, as illustrated in Figure 2.
Spencer's final claim in the interview is also entirely false.
"...the warming has been only 50% of what the consensus of climate models say it should be"
It's hard to know where this statement comes from – perhaps from Spencer's fellow climate scientist 'skeptic' Richard Lindzen, who often makes a similar claim. Regardless, this claim is just flat-out ridiculously wrong.
In reality, the observed global warming has been spot-on consistent with climate model projections. For example, the models used in the IPCC reports have been very accurate – much more accurate than predctions by Spencer's fellow 'skeptics' (Figure 3).
Figure 3: IPCC temperature projections (red, pink, orange, green) and contrarian projections (blue and purple) vs. observed surface temperature changes (average of NASA GISS, NOAA NCDC, and HadCRUT4; black and red) for 1990 through 2012.
Overall, Spencer made very few factually correct statements in this interview. The majority of his comments consisted of repeating long-debunked myths that any decent climate scientist should know are untrue. The amount of misinformation he conveyed was on par with what we would expect from a climate contrarian blogger.
Unfortunately, the Catholic Online readership will come away from this interview with a poorer understanding of the climate than they began with. A climate scientist should be able to do far better than this.
Spencer's interview included one more myth, about the costs of renewable and fossil fuel energy. For a bonus myth debunking, see Climate Consensus - the 97%.
Posted by dana1981 on Wednesday, 1 May, 2013
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