Arctic amplification means that surface temperatures in the high northern latitudes are rising faster than elsewhere. The reasons for this include positive feedbacks from the reduced ice cover as the world heats up.
Anthony Watts has announced that he's an Arctic amplification denier (archived here). He doesn't "believe" this is happening:
Actually, I don't think Anthony knows what Arctic amplification is. In his blog article at WUWT today, he was writing about a new paper on the Greenland melt of 2015, saying:
And in this case, they are citing a single event to claim “Arctic amplification” has set in.There are all sorts of things wrong with that sentence.
First of all, the paper that he is referring to doesn't make that claim at all. The authors, a team led by Marco Tedesco, already know that Arctic temperatures are rising faster and higher than temperatures elsewhere. They know already that Arctic amplification is real. It was in evidence before the 2015 event over Greenland. What they did say was that the weather patterns seen in Greenland in 2015 were consistent with what may be expected with Arctic amplification. They wrote about an observed persistent atmospheric ridge that was unprecedented since 1948 at least, saying that a number of things could have contributed to it:
The mechanisms that created and maintained the 2015 observed ridge may be linked with forcing from very strong extratropical cyclones 14, to forcings from southern regions 15 or to latent heat release 16. Another possibility is the local forcing related to Arctic amplification 13, 17. Although recent melt records over the Greenland have been linked to exceptional mid-tropospheric atmospheric conditions, with episodes of atmospheric blocking ridges being associated with Greenland’s melting extremes 9, 12, little or no attention has been given to the impact of the anticipated effects of Arctic amplification on the surface mass balance of the Greenland ice sheet. In this regard, the 2015 records for both the 500 hPa zonal winds and the maximum ridging latitude are consistent with the proposed effects on upper level atmosphere characteristics associated with Arctic amplification 13, 17.Anthony Watts, who has just accused volunteer weather recorders in the USA of faking data, wouldn't know an amplified temperature in the Arctic if fell over it. That much is obvious from his mixed up, confused lead in to the press release he copied and pasted.
Anthony also demonstrated a distinct lack of comprehension, contradicting himself in the process. The press release had this paragraph, which Anthony objected to:
The new study, published this week in Nature Communications, shows that those anticipated effects occurred over northern Greenland during the summer of 2015, including a northern swing of the jet stream that reached latitudes never before recorded in Greenland at that time of year.Anthony complained, writing:
Plus, they make the claim:
Jet stream reached northern latitudes never before recorded
We don’t have reliable weather maps that can accurately portray the position of the jet stream over Greenland prior to World War II, when the phenomenon was observed, as this reference in Wikipedia notes: ...
...It wasn’t until around 1950, that it began to be tracked regularly, so the “never before recorded” claim really doesn’t mean much in the scope of weather patterns for Greenland when you only have about 60 years of data.
Did he not just agree that it couldn't have been recorded before WWII, because of the lack of reliable weather maps? Did he miss the word "recorded"? In the paper, which Anthony didn't bother reading or trying to understand before he vented, the authors were more explicit, putting a time period on their "never before":
The unprecedented (1948–2015) and sustained atmospheric conditions promoted enhanced runoff, increased the surface temperatures and decreased the albedo in northern Greenland, while inhibiting melting in the south, where new melting records were set over the past decade.WUWT is a real waste of cyberspace isn't it. If you want disinformation and gobbledegook, or a climate conspiracy theory, WUWT is for you. If you want to study the psychology of deniers, then WUWT is an open book. If you want to learn about climate, go elsewhere.
Anthony continued as if he hoped some stray loser might think he knew what he was talking about:
The recent conditions in Greenland likely do not represent an aberrant fluctuation in the region’s climate or the beginning of “Arctic amplification”. Instead, events like the summer of 2015 lie within the known limits of natural variations that just haven’t been seen in the 60+ years of jet stream position data we are aware of.How does Anthony know that it's within the known limits of natural variations? He provides no evidence to support his claim. It's the opposite. He admits he has no evidence. He is getting more and more desperate to deny global warming as Greenland melts and the world gets ever hotter.
The paper is a bit heavy going, but you can read it here. The press release covers it fairly well. Here's some of it:
Arctic amplification, in the simplest terms, is the faster warming of the Arctic compared to the rest of the Northern Hemisphere as sea ice disappears. It is fueled by a feedback loop: rising global temperatures are melting Arctic sea ice, leaving dark open water that absorbs more solar radiation, and that warms the Arctic even more. Arctic amplification is well documented, but its effects on the atmosphere are more widely debated. One hypothesis suggests that the shrinking temperature difference between the Arctic and the mid-latitudes will lead to a slowing of the jet stream, which circles the northern latitudes and normally keeps frigid polar air sharply separated from warmer air in the south. Slower winds could create wilder swings of the jet stream, allowing warm, moist air to penetrate farther north....
..."How much and where Greenland melts can change depending on how things change elsewhere on earth," said lead author Marco Tedesco, a research professor at Columbia University's Lamont-Doherty Earth Observatory and adjunct scientist at NASA Goddard Institute for Space Studies. "If loss of sea ice is driving changes in the jet stream, the jet stream is changing Greenland, and this, in turn, has an impact on the Arctic system as well as the climate. It's a system, it is strongly interconnected and we have to approach it as such."
The Greenland ice sheet, earth's second largest after Antarctica, holds enough ice that, if it were to melt entirely, it would raise average global sea level by about seven meters. Understanding the drivers of melting is critical to understanding how quickly and by how much sea level will rise in the future and how Greenland's freshwater runoff will affect ocean circulation and ecology.
Northwest Greenland's summer of melt started in June 2015, when a high-pressure ridge squeezed off from the jet stream, the study shows. It moved westward over Greenland until it sat over the Arctic Ocean and affected weather across the island through mid-July.
That high-pressure system, called a cut-off high, brought clear skies and warmed northern Greenland, helping set records for surface temperature and meltwater runoff in the northwest, the study shows. With less summer snow falling and melting underway, northern Greenland's albedo, or reflectivity, also decreased. A less-reflective surface absorbs more solar energy, which feeds more melting, as Tedesco illustrated in a study earlier this year on the darkening of Greenland.
Northern Greenland also set an unusual July record for wind: the winds blew east to west on average, rather the usual west to east; only two other years on record show easterly winds on average in July, both slower. At the same time, the jet stream's northernmost ridge swung farther north than ever recorded for that month, passing 76 degrees North latitude, nearly 2 degrees farther north than the previous July record, set in 2009, the authors write.
The same atmospheric pattern had a different impact on southern Greenland, where new melting records have been set over the past decade. The south saw more snow during summer of 2015 and less melting than previous years.
The authors stop short of confirming Arctic amplification as the cause of the warming, but they say the results fit the anticipated effects of Arctic amplification described by Jennifer Francis of Rutgers University and Stephan Vavrus of the University of Wisconsin in a 2012 paper.
Recent studies exploring the potential effects of Arctic amplification have showed that high-pressure blocks connected to northward swings of the jet stream have become more common near Greenland. Edward Hanna of the University of Sheffield, a co-author of the new Nature Communications paper, released a study in May using the Greenland Blocking Index to measure the strength of stationary high-pressure systems over the past 165 years and found that seven of the top 11 systems had occurred since 2007.
"The significant increase in Greenland high-pressure blocking that has occurred in the last 20 to 30 years is clearly related to recent record warming over the region, as well as jet-stream changes," Hanna said. "This makes it more likely than not that within the next five to 10 years we will witness further record Greenland melt events like in 2012 and 2015."
"The Arctic is full of climate surprises, and Greenland is a key player," said James Overland, an oceanographer and climate scientist at the National Oceanic and Atmospheric Administration who was not involved in the new study. "Climate models suggest a 4 degree Celsius Arctic temperature increase by mid-century, but such jet stream related surprises acting on Greenland as reported by Tedesco et al. can accelerate Arctic climate change."
Whether the patterns seen in 2015 will continue in the future remains to be seen. This spring, Arctic sea ice set another record low for its maximum extent for the year. "Greenland also experienced early season melt in early April of this year comparable to April 2012. Record setting melt occurred later that summer, but it is too early to tell whether the same will hold true in 2016," said co-author Thomas Mote of the University of Georgia.
"The conditions we saw in the past aren't necessarily the conditions of the future," Tedesco said. "If humans change the forcing, we are going into uncharted territory."
As you can see, the authors are not only much more knowledgeable than Anthony Watts, failed weather announcer, they are also much more circumspect. They are scientists. Anthony Watts is a science denier.
From the WUWT comments
I've taken a second grab of the WUWT article to collect a few more comments. The first one is a beauty.
On a blog that typically cherry picks very short periods to claim "no warming", Tom Halla complains that 65 years is too short:
June 9, 2016 at 7:21 am
Sixty-five years does seem to be an inadequate peiod to study something as erratic as the jet stream.
RHS didn't bother reading the open source paper either, so he missed the reference to 1948-2015, and wrote:
June 9, 2016 at 8:10 am
When alarmists present “ever” as the timeframe, it is presented in the context of hundreds and thousands of years. It would be more accurate if they were to state “in our record set of 65 years, this has never been recorded”. They are creating a lie of omission through either incompetence, intent, or laziness. Either way, their timeframes are horribly misleading.
Rudd Istvan reckons that if a scientist works at a prestigious university like Columbia, then they must be a communist and therefore their work is not to be trusted. Typical of right wing authoritarian followers of the conspiratorial (and political) kind, ristvan wrote:
June 9, 2016 at 9:24 am
Consider the sources. Tedesco is joint at Columbia Lamont and GISS. Core warmunist institutions. Not surprising that they take a single blocking high weather event and claim unprecedented CAGW. Its their standard MO.
References and further reading
M. Tedesco, T. Mote, X. Fettweis, E. Hanna, J. Jeyaratnam, J. F. Booth, R. Datta & K. Briggs. "Arctic cut-off high drives the poleward shift of a new Greenland melting record." Nature Communications 7, Article number: 11723 doi:10.1038/ncomms11723 (open access)
Greenland's 2015 melt records consistent with 'Arctic amplification' - press release at ScienceDaily.com