2013 SkS News Bulletin #17: Cowtan and Way (2013)

Exposed: The myth of the global warming 'pause'
Global warming hasn’t stopped, new data finds
Global warming proponents and sceptics agree on one point: study into myth of 'pause' merits more research
Global warming since 1997 more than twice as fast as previously estimated
Media ignore study finding globe is warming twice as fast as thought
Missing data from Arctic one cause of pause in temperature rise
Our work is unlikely to be last word on slowdown, say authors of new paper
Planet warming much faster than previously thought
Recent surface warming has probably been underestimated
Recent warming may have been dramatically underestimated
Revised global warming models needed as data gap filled
Typhoon Haiyan must spur us on to slow climate change

Exposed: The myth of the global warming 'pause'

Scientists can now explain the “pause” in global warming that sceptics have used to bolster their arguments. Sceptics had claimed we have nothing to fear from climate change because it has stopped being a problem.

A new study has found that global temperatures have not flat-lined over the past 15 years, as weather station records have been suggesting, but have in fact continued to rise as fast as previous decades, during which we have seen an unprecedented acceleration in global warming.

The findings will undermine the arguments of leading sceptics, such as the former Chancellor Lord Lawson, who have criticised scientists from the Met Office and other climate organisations for not accepting that global warming has stopped since about 1998.

Global warming hasn’t stopped, new data finds

New research by scientists at the University of Ottawa and the University of York in the United Kingdom believe they have found the missing heat in global climate models.

Many climate-change skeptics look to data that suggest that there has been a pause in global warming since 1997. Temperatures from 1997 to 2010 have barely increased according to current datasets.

However, due to the limits of global weather stations, there are important gaps in data that make the models incomplete. The Arctic and Antarctic are two such places.

Dr. Kevin Cowtan of the University of York, along with PhD student and cyrosphere specialist – someone who studies ice – Robert Way of the University of Ottawa, used satellite data to fill in the missing gaps.

Global warming proponents and sceptics agree on one point: study into myth of 'pause' merits more research

A study suggesting that the "pause" in global warming is not real has managed to unify climate scientists and their arch-sceptics over the need for further research to clarify whether global average temperatures really have flat-lined over the past 15 years.

Global warming since 1997 more than twice as fast as previously estimated

A new paper published in The Quarterly Journal of the Royal Meteorological Society fills in the gaps in the UK Met Office HadCRUT4 surface temperature data set, and finds that the global surface warming since 1997 has happened more than twice as fast as the HadCRUT4 estimate. This short video abstract summarizes the study's approach and results.

The study, authored by Kevin Cowtan from the University of York and Robert Way from the University of Ottawa (who both also contribute to the climate science website Skeptical Science), notes that the Met Office data set only covers about 84 percent of the Earth's surface. There are large gaps in its coverage, mainly in the Arctic, Antarctica, and Africa, where temperature monitoring stations are relatively scarce. These are shown in white in the Met Office figure below. Note the rapid warming trend (red) in the Arctic in the Cowtan & Way version, missing from the Met Office data set.

Media ignore study finding globe is warming twice as fast as thought

After hyping an alleged "pause" in global warming, mainstream media have entirely ignored a groundbreaking study finding that warming over the last 16 years has actually proceeded at the same rate as it has since 1951 with no "pause" compared to that time period.

The study, published in the Quarterly Journal of the Royal Meteorological Society by Dr. Kevin Cowtan of the University of York and Robert Way of the University of Ottawa, found that the average global surface temperature has warmed 0.12 degrees Celsius between 1997 and 2012 (see the bold "Global" line in the graph above) -- two and a half times the UK Met Office's estimate of 0.05°C (see "Met Office" line). According to the new estimate, over the last 16 years the globe has warmed at the same rate as it has since 1951.

Writing about the study at the scientific blog Real Climate, climate scientist Stefan Rahmstorf concluded that the public debate about the "pause" has "become"completely baseless"and that any speed bump in warming is "not surprising" with natural variability:

Missing data from Arctic one cause of pause in temperature rise

The keepers of such long-term data sets, usually government institutions, know they have to account for numerous variations to keep a consistent measurement of temperatures through time. Without that, it is impossible to know how our world is changing.

Yet today's thermometers are not the same as those 100 years ago. The time of day that temperature measurements are taken has changed. Then there's the issue of coverage -- where, exactly, those thermometers are located. In more remote places, there are fewer measurements.

Our work is unlikely to be last word on slowdown, say authors of new paper

Recent research suggesting the so-called slowdown in surface warming might be less than previously thought has been met with interest from both climate scientists and skeptics. We hear from the authors about some of the queries raised and why they think their research is not the final say on whether or not the "slowdown" is real.

Planet warming much faster than previously thought

The planet may be warming much more – and much faster – in recent years than many experts have believed, according to a new study released this week by the U.K.-based Royal Meteorological Society.

Prepared by British and Canadian researchers, the study reports that the rise in global temperaturesover the past 15 years has been significantly underestimated due to gaps in temperature data around the world, largely in Earth's polar regions.

“It turns out that we only have surface measurements over about 84 percent of the globe," said Weather Underground's Dr. Jeff Masters, noting that there are no direct measurements oftemperatures in places like the Arctic even today, especially across its vast stretches of sea ice.

Recent surface warming has probably been underestimated

If you want to take someone’s temperature to see if they have a fever, you know where to put the thermometer. (Sorry, infants.) But where do you take the temperature of Earth’s climate? Inconveniently, the answer is “everywhere”—you need measurements covering the planet to properly calculate the global average surface temperature. That’s no big deal for Europe, where a local weather station is never far away, but it's much more of a problem for the North and South Poles where records are hard-won. A new analysis shows that how you deal with this problem makes a difference in what temperature you end up reading.

Building a global temperature dataset is a huge undertaking, because that’s only the half of it. Lots of careful corrections need to be made to the raw measurements to account for things like instrument changes, weather station placement, and even the time of day the station is checked.

One of the most commonly used datasets, dubbed “HadCRUT4” in its current incarnation, is maintained by the UK Met Office and researchers at the University of East Anglia. That dataset lacks temperature records over 16 percent of the globe, mostly parts of the Arctic, Antarctic, and Africa. Each group that manages one of these datasets faces this problem but deals with it a little differently. In HadCRUT4, the gaps are simply dropped out of the calculated average; in NASA’s GISTEMP dataset, these holes are filled in by interpolating from the nearest measurements.

The new study by Kevin Cowtan of the University of York and Robert Way of the University of Ottawa evaluates a few different methods for dealing with these gaps and shows that HadCRUT4 has probably been off by an important amount over the last few years.

Recent warming may have been dramatically underestimated

The so-called global warming "pause"—in essence, the contention that global warming has slowed down or even stopped over the past 15 years—drew dramatic media attention. Arguably, it derailed the entire rollout of the U.N. Intergovernmental Panel on Climate Change's Fifth Assessment Report back in late September.

All that....and yet a new study in the Quarterly Journal of the Royal Meteorological Society suggests there might not have even been a global warming "pause" at all. Rather, the notion of a "pause" may just be the result of incomplete data: In particular, a lack of weather stations in the remote Arctic region. That gap is problematic because we know that Arctic amplification is occurring and global warming is moving particularly fast there. The dramatic new low in Arctic sea ice extent in the year 2012 put an exclamation point on that finding.

Revised global warming models needed as data gap filled

A recent study using new techniques has filled in some of the information gaps in global temperatures and predictions of warming, and counters claims that warming has levelled off.

The interdisciplinary team of computational scientist Kevin Cowtan of the University of York in England, and cryosphere specialist and PhD candidate Robert Way of Canada, say that using satellites they have filled in large areas of the earth not covered by observational monitoring.

This previous “gap” in data has always resulted in skewed and underestimated reports and projections of what is really happening.

Typhoon Haiyan must spur us on to slow climate change

But what about the global warming pause much beloved by sceptics? There are always variations due to solar activity and other effects, but a new study by British and Canadian scientists Kevin Cowtan and Robert G Waycasts doubt on any pause. It suggests that the global temperature rise of the last 15 years has been greatly underestimated.

The reason is the data gaps in the weather station network, especially in the Arctic. If you fill these data gaps using satellite measurements, the warming trend is more than doubled, and the pause disappears. The trend of the last decade looks exactly the same as the trend since the 1950s.