Climate Medicine

Climate Quakery

As Richard Lindzen predicted, everyone wants on the climate bandwagon, because that is where the money is.  Medical scientists are pushing for their share of the pie, as evidenced by last week’s Met office gathering on Assessing the Global Impacts of Climate and Extreme Weather on Health and Well-Being. Not coincidentally, the 2nd Global Conference on Health and Climate was held July 7-8, 2016 in Paris.

The new field of Climate Medicine is evidenced by a slew of new organizations and studies.  In addition to numerous agencies set up within WHO and the UN, and governmental entities (such as the Met Office), there are many NGOs, such as:

Health Care Without Harm
Health and Environment Alliance
Health and Climate Foundation
Climate and Health Council
United States National Association of County and City Health Officials
Care International
Global Gender and Climate Alliance / Women’s Environment and   Development Organization
International Federation of Medical Students’ Associations
Climate Change and Human Health Programme, Columbia U.
Center for Health and the Global Environment, Harvard
National Center for Epidemiology and Population Health, ANC Canberra
Centre for Sustainability and the Global Environment, U of Wisconsin
Environmental Change Institute, Oxford
London School of Tropical Medicine and Hygiene, London, UK
International Human Dimensions Programme on Global Environmental Change, US National Academies of Science
US Climate and Health Alliance
Etc, etc., etc.

Of course, they are encouraged and abetted by the IPCC.

climatechange-infographic2

From the Fifth Assessment Report:

Until mid-century, projected climate change will impact human health mainly by exacerbating health problems that already exist (very high confidence). Throughout the 21st century, climate change is expected to lead to increases in ill-health in many regions and especially in developing countries with low income, as compared to a baseline without climate change (high confidence). By 2100 for RCP8.5, the combination of high temperature and humidity in some areas for parts of the year is expected to compromise common human activities, including growing food and working outdoors (high confidence). {2.3.2}

In urban areas climate change is projected to increase risks for people, assets, economies and ecosystems, including risks from heat stress, storms and extreme precipitation, inland and coastal flooding, landslides, air pollution, drought, water scarcity, sea level rise and storm surges (very high confidence). These risks are amplified for those lacking essential infrastructure and services or living in exposed areas. {2.3.2}

Feared Climate Health Impacts Are Unsupported by Scientific Research

NIPCC has a compendium of peer-reviewed studies on this issue and provides these findings (here)

Key Findings: Human Health
• Warmer temperatures lead to a decrease in temperature-related mortality, including deaths associated with cardiovascular disease, respiratory disease, and strokes. The evidence of this benefit comes from research conducted in every major country of the world.

• In the United States the average person who died because of cold temperature exposure lost in excess of 10 years of potential life, whereas the average person who died because of hot temperature exposure likely lost no more than a few days or weeks of life.

• In the U.S., some 4,600 deaths are delayed each year as people move from cold northeastern states to warm southwestern states. Between 3 and 7% of the gains in longevity experienced over the past three decades was due simply to people moving to warmer states.

• Cold-related deaths are far more numerous than heat-related deaths in the United States, Europe, and almost all countries outside the tropics. Coronary and cerebral thrombosis account for about half of all cold-related mortality.

• Global warming is reducing the incidence of cardiovascular diseases related to low temperatures and wintry weather by a much greater degree than it increases the incidence of cardiovascular diseases associated with high temperatures and summer heat waves.

• A large body of scientific examination and research contradict the claim that malaria will expand across the globe and intensify as a result of CO2 -induced warming.

• Concerns over large increases in vector-borne diseases such as dengue as a result of rising temperatures are unfounded and unsupported by the scientific literature, as climatic indices are poor predictors for dengue disease.

• While temperature and climate largely determine the geographical distribution of ticks, they are not among the significant factors determining the incidence of tick-borne diseases.

• The ongoing rise in the air’s CO2 content is not only raising the productivity of Earth’s common food plants but also significantly increasing the quantity and potency of the many healthpromoting substances found in their tissues, which are the ultimate sources of sustenance for essentially all animals and humans.

• Atmospheric CO2 enrichment positively impacts the production of numerous health-promoting substances found in medicinal or “health food” plants, and this phenomenon may have contributed to the increase in human life span that has occurred over the past century or so.

• There is little reason to expect any significant CO2 -induced increases in human-health-harming substances produced by plants as atmospheric CO2 levels continue to rise.

Source: Chapter 7. “Human Health,” Climate Change Reconsidered II: Biological Impacts (Chicago, IL: The Heartland Institute, 2014).
Full text of Chapter 7 and references on Human health begins pg. 955 of the full report here

Summary

Advances in medical science and public health have  benefited billions of people with longer and higher quality lives.  Yet this crucial social asset has joined the list of those fields corrupted by the dash for climate cash. Increasingly, medical talent and resources are diverted into inventing bogeymen and studying imaginary public health crises.

Economists Francesco Boselloa, Roberto Roson and Richard Tol conducted an exhaustive study called Economy-wide estimates of the implications of climate change: Human health

After reviewing all the research and crunching the numbers, they concluded that achieving one degree of global warming by 2050 will, on balance, save more than 800,000 lives annually.

Not only is the warming not happening, we would be more healthy if it did.

Oh, Dr. Frankenmann, what have you wrought?

Footnote:  More proof against Climate Medicine

From: Gasparrini et al: Mortality risk attributable to high and low ambient temperature: a multicountry observational study. The Lancet, May 2015

Cold weather kills 20 times as many people as hot weather, according to an international study analyzing over 74 million deaths in 384 locations across 13 countries. The findings, published in The Lancet, also reveal that deaths due to moderately hot or cold weather substantially exceed those resulting from extreme heat waves or cold spells.

“It’s often assumed that extreme weather causes the majority of deaths, with most previous research focusing on the effects of extreme heat waves,” says lead author Dr Antonio Gasparrini from the London School of Hygiene & Tropical Medicine in the UK. “Our findings, from an analysis of the largest dataset of temperature-related deaths ever collected, show that the majority of these deaths actually happen on moderately hot and cold days, with most deaths caused by moderately cold temperatures.”

 

 

Average Arctic Melt July 7

In the chart below MASIE shows 2016 Mid-June  Arctic ice extent drew near to average and close to 2015, then dropped lower before again converging on average by the end.  Now in July 2016 is matching the average extent measured over the last ten years, 2006-2015.  With SII back on line, it was reporting similar extents during June (as it has in the past).  Recently it is starting to underestimate again, ~400k km2 lower. (SII and MASIE comparison is here.)

MASIE 2016 day188

Looking into the details, some marginal seas are melting earlier than last year, while the central, enduring ice pack is relatively unaffected.  In fact, a large difference between 2016 and 2015 comes from the losses from maximums in a single place: Sea of Okhotsk.  To date 1303k km2 of ice was lost this year vs. 753k km2 lost in 2015 in that sea at the same date.

Despite greater losses in Okhotsk, 2016 ice extent in July is fairly ordinary with slight differences across the regions.  At the present pace of declining ice extents, the last three days 2016 matches the ten-year average, and is four days ahead of 2015.

Comparing the Arctic ice extents with their maximums shows the melting is occurring mostly in the marginal seas, now including Kara Sea as expected in June.  Most of the additional ice loss in July comes from Baffin and Hudson Bays.

2016188 NH Max Loss % Loss Sea Max % Total Loss
 (0) Northern_Hemisphere 5880825 39.00% 100%
 (1) Beaufort_Sea 243265 22.73% 4%
 (2) Chukchi_Sea 214347 22.19% 3%
 (3) East_Siberian_Sea 26723 2.46% 0%
 (4) Laptev_Sea 35559 3.96% 1%
 (5) Kara_Sea 648206 69.33% 10%
 (6) Barents_Sea 589137 98.29% 10%
 (7) Greenland_Sea 300055 45.48% 5%
 (8) Baffin_Bay_Gulf_of_St._Lawrence 1266759 77.03% 20%
 (9) Canadian_Archipelago 88793 10.41% 1%
 (10) Hudson_Bay 533623 42.32% 9%
 (11) Central_Arctic 80724 2.49% 1%
 (12) Bering_Sea 768232 100.00% 12%
 (13) Baltic_Sea 97582 100.00% 2%
 (14) Sea_of_Okhotsk 1306657 99.84% 21%

It is clear from the above that the bulk of ice losses are coming from Okhotsk, Barents and Bering Seas (95+% melted), along with Kara Sea and Baffin Bay-St. Lawrence (70+% melted).  Hudson  Bay has lost 42% of max extent.  All of them are marginal seas that will go down close to zero by September.  Note: Some seas are not at max on the NH max day.  Thus, totals from adding losses will vary from NH daily total.

For additional context on Arctic melt see last Arctic Ice Watch June 30

 

 

 

 

Warm is Cold, and Down is Up

Paul Homewood has a post today: Who Is Lying? John Holdren, Jennifer Francis, Or NOAA?

The issue revolves around claims of global warming changing the jet stream, resulting in extreme weather, including colder winters in the US. That’s a neat trick: Getting global warming to produce cold weather.
.
Lying presumes they know the truth and speak falsely. This is more a case of saying what they believe but being wrong. (“Love of Theory is the Root of all Evil” –William Briggs)

Seasoned meteorologist Judah Cohen of AER sees it differently.

My colleagues, at AER and at selected universities, and I have found a robust relationship between two October Eurasian snow indices and the large-scale winter hemispheric circulation pattern known as the North Atlantic or Arctic Oscillation pattern (N/AO).

The N/AO is more highly correlated with or explains the highest variance of winter temperatures in eastern North America, Europe and East Asia than any other single or combination of atmospheric or coupled ocean-atmosphere patterns that we know of. Therefore, if we can predict the winter N/AO (whether it will be negative or positive) that provides the best chance for a successful winter temperature forecast in North America but certainly does not guarantee it.

He goes on to say that precipitation is the key, not air temperatures, and ENSO is a driving force:

As long as I have been a seasonal forecaster, I have always considered El Nino/Southern Oscillation (ENSO) as a better predictor of precipitation than temperature across the Eastern US. I think this is supported by the observational or statistical analysis as well as the skill or accuracy of the climate models.

There have been recent modeling studies that demonstrate that El Nino modulates the strength and position of the Aleutian Low that then favors stratospheric warmings and subsequently a negative winter N/AO that are consistent with our own research on the relationship between snow cover and stratospheric warmings. So the influence of ENSO on winter temperatures in the Mid-Atlantic and the Northeast may be greater than I acknowledge or that is represented in our seasonal forecast model.

Summary

As Cohen’s diagram shows, there is an effect from warming, but in the stratosphere. Global warming theory claims CO2 causes warming in the troposphere and cooling in the stratosphere. So whatever is going on, it is not due to CO2.

Cohen’s interview with the Washington Post.

its-easier-to-fool-people-than-to-convince-them-that-they-have-been-fooled

 

Climategate Redux?

The AAAS (American Association for the Advancement of Science) sent a letter on June 28, 2016 urging the US congress to act on climate change:

There is strong evidence that ongoing climate change is having broad negative impacts on society, including the global economy, natural resources, and human health. For the United States, climate change impacts include greater threats of extreme weather events, sea level rise, and increased risk of regional water scarcity, heat waves, wildfires, and the disturbance of biological systems. The severity of climate change impacts is increasing and is expected to increase substantially in the coming decades.

Those of us with short memories need to be reminded that the Climategate emails were triggered by an appeal to congress in 2009 by the AAAS. Dr. Arnd Bernaerts provides the background and the historical context.

On October 21, 2009 the AAAS letter included this:

Moreover, there is strong evidence that ongoing climate change will have broad impacts on society, including the global economy and on the environment. For the United States, climate change impacts include sea level rise for coastal states, greater threats of extreme weather events, and increased risk of regional water scarcity, urban heat waves, western wildfires, and the disturbance of biological systems throughout the country. The severity of climate change impacts is expected to increase substantially in the coming decades.
Full text provided by Dr. Bernaerts here, along with his response.

The Climategate Emails

2011 Report here
More than 5,000 documents have been leaked online purporting to be the correspondence of climate scientists at the University of East Anglia who were previously accused of ‘massaging’ evidence of man-made climate change.

Following on from the original ‘climategate’ emails of 2009, the new package appears to show systematic suppression of evidence, and even publication of reports that scientists knew to to be based on flawed approaches. 

The leaker of the emails “FOIA” said this in a comment at the time, Nov. 17, 2009:
We feel that climate science is, in the current situation, too important to be kept under wraps.
We hereby release a random selection of correspondence, code, and documents.
Hopefully it will give some insight into the science and the people behind it.

Dr. Bernaerts comments on the current situation:

I had hoped that the “endorsement” by “FOIA said” would give a helpful impulse to my complaint about a science which is not able to define what they are talking about, namely CLIMATE. Those not happy with the AGW discussion should have pressured WMO, IPCC and consorts to demonstrate that they are capable to do what every academic is trained to do, to provide reasonable and workable definitions. Unfortunately that did not materialize. The definition matter remains neglected by AGW supporters and sceptics alike. A great pity. A further conference paper from January 2010, available at: http://www.whatisclimate.com/ explains this in more detail.

What has changed in the world of AAAS and in the field of supporting and opposing views: Much too little. A pity that we cannot ask FOIA what would be his view today.

The Climate Lemmings
h/t Beth

The Coming Climate July 4 Update

Update July 4 below

When you see a graph like that below, it is obvious that an unusually strong El Nino just happened in our climate system. It resulted in higher global temperatures the last two years and so far in 2016. But that event is over now, and naturally we wonder what to expect in the months and years ahead.

cdas_v2_hemisphere_2016june2
For example some comments from a recent thread at WUWT (here) were intriguing:

It will be interesting to see what comes next. The major difference between the 1998 el nino and this one is that in 1998 the sun was increasing in solar activity, while this one solar activity is decreasing. (rishrac)

Nino3,4 and UAH LT dC Anomalies, and UAH LT Scaled *3 and Lagged 4 Months h/t Allan MacRae

And richard takes the long view of the situation:

While we all stare at the short-term ups and downs of the global temperatures, pay a little thought to the fact that the Earth’s orbit around the Sun causes snow in the winter and warmth during the summer, so it may be important?

Perihelion presently occurs around January 3, (Northern hemisphere winter, Southern summer) while aphelion is around July 4. Therefore, the southern hemisphere receives more solar radiation and is therefore warmer in summer and colder in winter (aphelion). The Northern hemisphere has cooler summers and milder winter (solar radiation-wise).

Also the northern hemispheres autumn and winter are slightly shorter than spring and summer, because the Earth is moving faster around the Sun in winter slower in summer.

This alone could account for “Global Warming” attributed to CO2, (which no doubt plays some part in it).

Over the next 10,000 years, northern hemisphere winters will become gradually longer and summers will become shorter, due to the change in the Earth’s Orbital Eccentricity.

Couple this with changes in the Earth’s tilt, which varies from 22.1 degrees to 24.5 degrees, (currently at 23.4 degrees). More tilt means more solar radiation gets to the poles (global warming) and less tilt means less radiation gets to the poles (global cooling). The last maximum tilt occurred in 8700 BC (Holocene maximum) and the next minimum tilt will happen in 11,800 AD (the advance of the ice sheets), precisely at the time of longer northern winters and shorter summers.

Orbital Climate Factors: E for eccentricity, T for tilt, and P for precession

Predicting the Future is Tough

Chiefio (E.M. Smith) has a good post (here) reminding us that statistical projections do not help us much in this case. Temperature series produced by our climate system have special qualities. The patterns are auto-correlated, meaning that tomorrow’s weather will be similar to today’s; the occurrence is not totally independent, like the flip of coin. IOW there is momentum in the climate characteristics, which can and do fluctuate over seasons, decades, centuries and more. Our attempts to use linear regressions to forecast are thwarted by temperature time series that do not follow a normal gaussian distribution, and are semi-chaotic and non-stationary.

Four Possibilities Forward From Today

From past experience, the next few years could logically follow one of four temperature scenarios:
1. The Plateau since 1998 continues.
2. The Warming prior to 1998 resumes.
3. A new Plateau begins with 2016 at a higher (step up) level.
4. A Cooling begins comparable to the years after 1940.

All of these have analogues in our recent climate observations. If this now finished El Nino triggers a regime change comparable to the 1998 event, then a step-up plateau can result. If warmists are right, and there is a release of pent-up heat in the system, then a warming trend would resume.

If this El Nino is not strong enough to shift the regime, then the Plateau could continue at the same level. Finally, it could be that several factors align to reverse the warming since the 1970’s, and bring a return to cooler 1950’s weather.

Those who see a quasi-60 year cycle in weather patterns note that it is about time for the PDO in the Pacific and the AMO in the Atlantic to be in cooler phases, along with a quiet sun, which went spotless last week. There are also those attending to orbital climate patterns, which gave us the Modern Warming Period and will eventually take it away.

 

Changes in climate due to earth’s orbit around the sun

Update July 4

In the previous thread is a chart from J. Martin displaying the effects of the changing tilt of earth’s axis.  As shown, the long term pattern is toward cooling.

J. Martin: Tilt (obliquity) has a 41k yr cycle and prior to the arrival of 100,000 year glaciations, the 41k year world dominated with short sharp glaciations every 41 thousand years. The 41k influence us still there. Javier has done a graph which overlays the obliquity cycle on top of a graph of the holocene which produces a perfect match. So it would seem that interstitial temperatures are largely governed by obliquity, but glaciation temperatures are governed by eccentricity with occasional disturbances from precession .

In addition, ren provides interesting links to studies showing SA (Sunspot numbers) correlating to Middle Ages Warm period and LIA, and a 2012 study forecasting the next 2 cycles.

shepherd etalfig1

Figure 1. Bottom plot: the summary component of the two PCs (solid curve) and the decaying component (dashed curves) for the “historical” data (cycles 21–23) and predicted data (cycles 24–26). The cycle lengths (about 11 yr) are marked with different colors.

Abstract: We can conclude with a sufficient degree of confidence that the solar activity in cycles 24–26 will be systematically decreasing because of the increasing phase shift between the two magnetic waves of the poloidal field leading to their full separation into opposite hemispheres in cycles 25 and 26. This separation is expected to result in the lack of their subsequent interaction in any of the hemispheres, possibly leading to a lackof noticeable sunspot activity on the solar surface lasting for a decade or two, similar to those recorded in the medieval period.

Again, to the extent that SSNs are a proxy for changes in heat content within the earth’s climate system, the graph is also indicating future cooling.

For an approach to quantifying climate effects from Solar Activity, as well as oceanic cycles, see:
Quantifying Natural Climate Change

Arctic Ice Watch June 30

In the chart below MASIE shows 2016 Mid-June  Arctic ice extent drew near to average and close to 2015, then dropped lower before again converging on average by the end.  With SII back on line, it is reporting similar extents during June (as it has in the past), though it appears to start underestimating again. (SII and MASIE comparison is here.)

MASIE 2016 day182
This year and last had the same average extents until May when a gap opened up associated with the Beaufort gyre high winds breaking up and moving ice to create 150 k km2 open water in that sea. The difference in Beaufort Sea had reduced to ~45 k below average, but the gap has reopened the last 2 days to ~125 k.

Looking into the details, some marginal seas are melting earlier than last year, while the central, enduring ice pack is relatively unaffected.  In fact, a large difference between 2016 and 2015 comes from the losses from maximums in a single place: Sea of Okhotsk.  To date 1303k km2 of ice was lost this year vs. 753k km2 lost in 2015 in that sea at the same date.

Despite greater losses in Okhotsk, 2016 ice extent in June is fairly ordinary with slight differences across the regions.  At the present pace of declining ice extents, 2016 is running three days ahead of the ten-year average, and six days ahead of 2015.

US Navy predicts summer ice free Arctic by 2016 Greenpeace icebreaking ship, Arctic Sunrise, among broken floes of Arctic sea ice, photographed from the air. This image was taken in the Fram Strait. Good to see Greenpeace doing their bit to create more open water.

US Navy predicts summer ice free Arctic by 2016. Greenpeace icebreaking ship, Arctic Sunrise, among broken floes of Arctic sea ice, photographed from the air. This image was taken in the Fram Strait. Greenpeace doing their bit to create more open water.

As the chart below shows, the seas most down from average this year are Beaufort, Kara, Barents, and Greenland Sea.  Meanwhile higher extents are showing in Chukchi, East Siberian, Laptev, and Hudson Bay, resulting in 2016 below average.

Region 2016182 Day 182
Average
2016-Ave.
 (0) Northern_Hemisphere 9496516 9736362 -239846
 (1) Beaufort_Sea 792915 920245 -127329
 (2) Chukchi_Sea 775436 734342 41094
 (3) East_Siberian_Sea 1065714 1023242 42472
 (4) Laptev_Sea 863015 713555 149460
 (5) Kara_Sea 362414 561945 -199531
 (6) Barents_Sea 25988 110950 -84962
 (7) Greenland_Sea 367846 518951 -151105
 (8) Baffin_Bay_Gulf_of_St._Lawrence 465379 483472 -18093
 (9) Canadian_Archipelago 791274 774241 17033
 (10) Hudson_Bay 803437 658144 145293
 (11) Central_Arctic 3176041 3211595 -35554
 (12) Bering_Sea 0 6730 -6730
 (13) Baltic_Sea 0 6 -6
 (14) Sea_of_Okhotsk 5914 17526 -11612

Comparing the Arctic ice extents with their maximums shows the melting is occurring mostly in the marginal seas, now including Kara Sea as expected in June.

2016182 NH Max Loss % Loss Sea Max % Total Loss
 (0) Northern_Hemisphere 5581083 37.02% 100%
 (1) Beaufort_Sea 277530 25.93% 5%
 (2) Chukchi_Sea 190553 19.73% 3%
 (3) East_Siberian_Sea 21406 1.97% 0%
 (4) Laptev_Sea 34794 3.88% 1%
 (5) Kara_Sea 572574 61.24% 10%
 (6) Barents_Sea 573391 95.66% 10%
 (7) Greenland_Sea 291866 44.24% 5%
 (8) Baffin_Bay_Gulf_of_St._Lawrence 1179203 71.70% 20%
 (9) Canadian_Archipelago 61904 7.26% 1%
 (10) Hudson_Bay 457434 36.28% 8%
 (11) Central_Arctic 70669 2.18% 1%
 (12) Bering_Sea 768232 100.00% 13%
 (13) Baltic_Sea 97582 100.00% 2%
 (14) Sea_of_Okhotsk 1302782 99.55% 22%

It is clear from the above that the bulk of ice losses are coming from Okhotsk, Barents and Bering Seas (95+% melted),along with Kara Sea and Baffin Bay-St. Lawrence (60+% melted).  All of them are marginal seas that will go down close to zero by September.  Note: Some seas are not at max on the NH max day.  Thus, totals from adding losses will vary from NH daily total.

CPC shows the Arctic Oscillation waffling between positive and negative values, recently positive and forecasted to near neutral. Generally, positive AO signifies lower pressures over Arctic ice, with more cloud, lower insolation and less melting.  The outlook at this point is mixed.

September Minimum Outlook

Historically, where will ice be remaining when Arctic melting stops? Over the last 10 years, on average MASIE shows the annual minimum occurring about day 260. Of course in a given year, the daily minimum varies slightly a few days +/- from that.

For comparison, here are sea ice extents reported from 2007, 2012, 2014 and 2015 for day 260:

Arctic Regions 2007 2012 2014 2015
Central Arctic Sea 2.67 2.64 2.98 2.93
BCE 0.50 0.31 1.38 0.89
Greenland & CAA 0.56 0.41 0.55 0.46
Bits & Pieces 0.32 0.04 0.22 0.15
NH Total 4.05 3.40 5.13 4.44

Notes: Extents are in M km2.  BCE region includes Beaufort, Chukchi and Eastern Siberian seas. Greenland Sea (not the ice sheet). Canadian Arctic Archipelago (CAA).  Locations of the Bits and Pieces vary.

As the table shows, low NH minimums come mainly from ice losses in Central Arctic and BCE.  The great 2012 cyclone hit both in order to set the recent record. The recovery since 2012 shows in 2014, with some dropoff last year, mostly in BCE.

Summary

We are well into the melt season, and the resulting minimum will depend upon the vagaries of weather between now and September.  Early on, 2016 was slightly higher than 2015 in March, lower in May and now closing the gap. Note: 2016 melt season is starting without the Blob, with El Nino over, and a cold blob in the North Atlantic.  The AO has been hovering around neutral, now possibly indicating cloud cover reducing the pace of melting.

Meanwhile we can watch and appreciate the beauty of the changing ice conditions.

 

Arctic Reflection: Clouds replace snow and ice as solar reflector NASA photo

Footnote:  Regarding the colder than normal water in the North Atlantic

A 2016 article for EOS is entitled Atlantic Sea Ice Could Grow in the Next Decade

Changing ocean circulation in the North Atlantic could lead to winter sea ice coverage remaining steady and even growing in select regions.

The researchers analyzed simulations from the Community Earth System Model, modeling both atmosphere and ocean circulation. They found that decadal-scale trends in Arctic winter sea ice extent are largely explained by changes in ocean circulation rather than by large-scale external factors like anthropogenic warming.

From the Abstract of Yeager et al.

We present evidence that the extreme negative trends in Arctic winter sea-ice extent in the late 1990s were a predictable consequence of the preceding decade of persistent positive winter North Atlantic Oscillation (NAO) conditions and associated spin-up of the thermohaline circulation (THC). Initialized forecasts made with the Community Earth System Model decadal prediction system indicate that relatively low rates of North Atlantic Deep Water formation in recent years will result in a continuation of a THC spin-down that began more than a decade ago. Consequently, projected 10-year trends in winter Arctic winter sea-ice extent seem likely to be much more positive than has recently been observed, with the possibility of actual decadal growth in Atlantic sea-ice in the near future.