New Research

[knocker]

New visualizations highlight new information on the contrasting Arctic and Antarctic sea-ice trends since the late 1970s

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Month-by-month ranking of 37 years (1979–2015) of satellite-derived sea-ice extents in the Arctic and Antarctic reveals interesting new details in the overall trends toward decreasing sea-ice coverage in the Arctic and increasing sea-ice coverage in the Antarctic. The Arctic decreases are so definitive that there has not been a monthly record high in Arctic sea-ice extents in any month since 1986, a time period during which there have been 75 monthly record lows. The Antarctic, with the opposite but weaker trend toward increased ice extents, experienced monthly record lows in 5 months of 1986, then 6 later monthly record lows scattered through the dataset, with the last two occurring in 2006, versus 45 record highs since 1986. However, in the last three years of the 1979–2015 dataset, the downward trends in Arctic sea-ice extents eased up, with no new record lows in any month of 2013 or 2014 and only one record low in 2015, while the upward trends in Antarctic ice extents notably strengthened, with new record high ice extents in 4 months (August–November) of 2013, in 6 months (April–September) of 2014, and in 3 months (January, April, and May) of 2015. Globally, there have been only 3 monthly record highs since 1986 (only one since 1988), whereas there have been 43 record lows, although the last record lows (in the 1979–2015 dataset) occurred in 2012.

http://www.sciencedirect.com/science/article/pii/S0034425716302218

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El Niño drives record rise in atmospheric carbon dioxide

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13 June 2016 - The rising concentration of atmospheric carbon dioxide has passed a symbolic threshold early due to the fastest annual increase on record

The human-caused rise in the atmospheric concentration of carbon dioxide is being given an extra boost this year by the natural climate phenomena of El Niño say climate scientists in a paper published in today's edition of the journal: Nature Climate Change. As a result, 2016 will be the first year with concentrations above 400 parts per million (ppm) all year round in the iconic Mauna Loa carbon dioxide record.

Prof Richard Betts, of the Met Office Hadley Centre and University of Exeter, is the lead author on the paper. He said: "The atmospheric carbon dioxide concentration is rising year-on-year due to human emissions, but this year it is getting an extra boost due to the recent El Niño event. This warms and dries tropical ecosystems, reducing their uptake of carbon, and exacerbating forest fires. Since human emissions are now 25% greater than in the last big El Niño in 1997/98, this all adds up to a record CO2 rise this year."

http://www.metoffice.gov.uk/news/releases/2016/MaunaLoaCO2_2016?utm_source=twitterfeed&utm_medium=twitter

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Arctic Freshwater Synthesis: Summary of key emerging issues

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In response to a joint request from the World Climate Research Program's Climate and Cryosphere Project, the International Arctic Science Committee, and the Arctic Council's Arctic Monitoring and Assessment Program an updated scientific assessment has been conducted of the Arctic Freshwater System, entitled the Arctic Freshwater Synthesis (AFS). The major reason behind the joint request was an increasing concern that changes to the Arctic Freshwater System have produced, and could produce even greater, changes to biogeophysical and socioeconomic systems of special importance to northern residents and also produce extra-Arctic climatic effects that will have global consequences. The AFS was structured around six key thematic areas: atmosphere, oceans, terrestrial hydrology, terrestrial ecology, resources, and modeling, the review of each coauthored by an international group of scientists and published as separate articles in this special section of Journal of Geophysical Research: Biogeosciences. This AFS summary article reviews key issues that emerged during the conduct of the synthesis, especially those that are cross-thematic in nature, and identifies future research required to address such issues.

http://onlinelibrary.wiley.com/doi/10.1002/2015JG003128/full

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Scientists say Greenland’s vast melt hasn’t slowed down the Atlantic Ocean’s circulation — yet

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Last year, a bombshell scientific study suggested a scenario that has long worried scientists was coming to pass: a slowdown in the North Atlantic ocean currents that usually redistribute warm and cold waters, thanks to massive ice melts in Greenland and other Arctic changes.

If this is really happening, it’s a big deal. The circulation, sometimes called the Atlantic meridional overturning circulation or AMOC, transports enormous amounts of warmth northward from lower latitudes. If it slows down, there will be less heat transport to Europe and higher latitudes, as well as key consequences for warming and sea level rise along the U.S. east coast.

However, this is a vast, enormously complicated and inadequately studied ocean system, and there are well-known patterns of natural variability in the Atlantic that could also drive things. Indeed, the circulation had already been observed to be slowing over the past decade, but it is less clear whether this slowdown is the result of climate change or, simply, part of that variability (or both).

And now, in the journal Nature Geoscience, a new paper has emerged suggesting that while Greenland has already contributed enough water to the ocean to begin to freshen seas  (specifically, the Labrador Sea between Greenland and Baffin Island), there hasn’t been enough freshwater yet to slow the AMOC, which is driven by differences in the density of cold and warm salt water.

https://www.washingtonpost.com/news/energy-environment/wp/2016/06/20/a-huge-science-debate-is-brewing-over-whether-weve-messed-up-the-atlantic-oceans-circulation/?postshare=2701466439195522&tid=ss_tw

[knocker]

The North Atlantic Oscillation as a driver of rapid climate change in the Northern Hemisphere

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Pronounced climate changes have occurred since the 1970s, including rapid loss of Arctic sea ice1, large-scale warming2 and increased tropical storm activity3 in the Atlantic. Anthropogenic radiative forcing is likely to have played a major role in these changes4, but the relative influence of anthropogenic forcing and natural variability is not well established. The above changes have also occurred during a period in which the North Atlantic Oscillation has shown marked multidecadal variations5. Here we investigate the role of the North Atlantic Oscillation in these rapid changes through its influence on the Atlantic meridional overturning circulation and ocean heat transport. We use climate models to show that observed multidecadal variations of the North Atlantic Oscillation can induce multidecadal variations in the Atlantic meridional overturning circulation and poleward ocean heat transport in the Atlantic, extending to the Arctic. Our results suggest that these variations have contributed to the rapid loss of Arctic sea ice, Northern Hemisphere warming, and changing Atlantic tropical storm activity, especially in the late 1990s and early 2000s. These multidecadal variations are superimposed on long-term anthropogenic forcing trends that are the dominant factor in long-term Arctic sea ice loss and hemispheric warming.

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2738.html

[knocker]

Emergence of healing in the Antarctic ozone layer

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Industrial chlorofluorocarbons that cause ozone depletion have been phased out under the Montreal Protocol. A chemically-driven increase in polar ozone (or “healing”) is expected in response to this historic agreement. Observations and model calculations taken together indicate that the onset of healing of Antarctic ozone loss has now emerged in September. Fingerprints of September healing since 2000 are identified through (i) increases in ozone column amounts, (ii) changes in the vertical profile of ozone concentration, and (iii) decreases in the areal extent of the ozone hole. Along with chemistry, dynamical and temperature changes contribute to the healing, but could represent feedbacks to chemistry. Volcanic eruptions episodically interfere with healing, particularly during 2015 (when a record October ozone hole occurred following the Calbuco eruption).

http://science.sciencemag.org/content/early/2016/06/30/science.aae0061

[Polar Maritime]

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By Dr. Tony Phillips (Spaceweather.com)

Noctilucent clouds are such a mystery that in 2007 NASA launched a spacecraft to study them. The Aeronomy of Ice in the Mesosphere satellite (AIM) is equipped with sensors specifically designed to study the swarms of ice crystals that make up NLCs.  Researchers call these swarms “polar mesospheric clouds” (PMCs).

A new study published in the Journal of Geophysical Research (doi:10.1002/2015JD024439) confirms what some researchers have long suspected:  PMCs in the northern hemisphere have become more frequent and brighter in recent decades—a development that may be related to climate change. 

http://news.spaceweather.com/climate-change-at-the-edge-of-space/

Posted this in the NLC thread but also relevant here. 

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Attributing human mortality during extreme heat waves to anthropogenic climate change

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t has been argued that climate change is the biggest global health threat of the 21st century. The extreme high temperatures of the summer of 2003 were associated with up to seventy thousand excess deaths across Europe. Previous studies have attributed the meteorological event to the human influence on climate, or examined the role of heat waves on human health. Here, for the first time, we explicitly quantify the role of human activity on climate and heat-related mortality in an event attribution framework, analysing both the Europe-wide temperature response in 2003, and localised responses over London and Paris. Using publicly-donated computing, we perform many thousands of climate simulations of a high-resolution regional climate model. This allows generation of a comprehensive statistical description of the 2003 event and the role of human influence within it, using the results as input to a health impact assessment model of human mortality. We find large-scale dynamical modes of atmospheric variability remain largely unchanged under anthropogenic climate change, and hence the direct thermodynamical response is mainly responsible for the increased mortality. In summer 2003, anthropogenic climate change increased the risk of heat-related mortality in Central Paris by ~70% and by ~20% in London, which experienced lower extreme heat. Out of the estimated ~315 and ~735 summer deaths attributed to the heatwave event in Greater London and Central Paris, respectively, 64 (±3) deaths were attributable to anthropogenic climate change in London, and 506 (±51) in Paris. Such an ability to robustly attribute specific damages to anthropogenic drivers of increased extreme heat can inform societal responses to, and responsibilities for, climate change.

http://iopscience.iop.org/article/10.1088/1748-9326/11/7/074006 Open Access

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“Grey swan” cyclones predicted to be more frequent and intense

Study finds some coastal regions may face a risk of unprecedented storm surge in the next century.

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“Grey swan” cyclones — extremely rare tropical storms that are impossible to anticipate from the historical record alone — will become more frequent in the next century for parts of Florida, Australia, and cities along the Persian Gulf, according to a study published today in the journal Nature Climate Change.

In contrast with events known as “black swans” — wholly unprecedented and unexpected occurrences, such as the 9/11 attacks and the 2008 financial collapse — grey swans may be anticipated by combining physical knowledge with historical data.

In the case of extreme tropical cyclones, grey swans are storms that can whip up devastating storm surges, beyond what can be foreseen from the weather record alone — but which may be anticipated using global simulations, along with historical data.

In the current paper, authors Kerry Emanuel, the Cecil and Ida Green Professor in Earth and Planetary Sciences at MIT, and Ning Lin of Princeton University simulated the risk of grey swan cyclones, and their resulting storm surges, for three vulnerable coastal regions. They found a risk of such storms for regions such as Dubai, United Arab Emirates, where tropical storms have never been recorded. In Tampa, Florida, and Cairns, Australia — places that experience fairly frequent storms — storms of unprecedented magnitude will be more likely in the next century.

http://news.mit.edu/2015/grey-swan-cyclones-storm-surge-0831

An article on the subject by Jeff Masters

https://www.wunderground.com/blog/JeffMasters/extreme-grey-swan-hurricanes-in-tamp

[knocker]

Observed and simulated full-depth ocean heat-content changes for 1970–2005

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Abstract. Greenhouse-gas emissions have created a planetary energy imbalance that is primarily manifested by increasing
ocean heat content (OHC). Updated observational estimates of full-depth OHC change since 1970 are presented
that account for recent advancements in reducing observation errors and biases. The full-depth OHC has increased
by 0.74 [0.68, 0.80]1022 J yr1 (0.46Wm2/ and 1.22 [1.16–1.29]1022 J yr1 (0.75Wm2/ for 1970–2005 and
1992–2005, respectively, with a 5 to 95% confidence interval of the median. The CMIP5 models show large spread in
OHC changes, suggesting that some models are not state-of the- art and require further improvements. However, the ensemble
median has excellent agreement with our observational estimate: 0.68 [0.54–0.82]1022 J yr1 (0.42Wm2/
from 1970 to 2005 and 1.25 [1.10–1.41]1022 J yr1 (0.77Wm2/ from 1992 to 2005. These results increase confidence
in both the observational and model estimates to quantify and study changes in Earth’s energy imbalance over
the historical period. We suggest that OHC be a fundamental metric for climate model validation and evaluation, especially
for forced changes (decadal timescales).

http://www.ocean-sci.net/12/925/2016/os-12-925-2016.pdf

Paper discussed here

https://andthentheresphysics.wordpress.com/2016/07/28/full-depth-ohc/

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Is the detection of accelerated sea level rise imminent?

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Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era. Here, a combined analysis of altimeter data and specially designed climate model simulations shows the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred. This masking arose largely from a recovery in ocean heat content through the mid to late 1990 s subsequent to major heat content reductions in the years following the eruption. A consequence of this finding is that barring another major volcanic eruption, a detectable acceleration is likely to emerge from the noise of internal climate variability in the coming decade.

http://www.nature.com/articles/srep31245

Article

https://www.theguardian.com/environment/climate-consensus-97-per-cent/2016/aug/10/climate-scientists-make-a-bold-prediction-about-sea-level-rise

[knocker]

Not new research but some thoughts by Tamino on the Hansen 1981 paper.

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In 1981 James Hansen and colleagues published research in the prestigious peer-reviewed journal Science titled “Climate Impact of Increasing Atmospheric Carbon Dioxide.” They discussed the result of basic physics, that carbon dioxide in the air inhibits Earth cooling off, thus heating the planet. They also reported the results of computer simulations of Earth’s climate in a world with ever-increasing CO2.

https://tamino.wordpress.com/2016/08/16/crystal-serenity/

[Northernlights]

5 minutes ago, knocker said:

Not new research but some thoughts by Tamino on the Hansen 1981 paper.

https://tamino.wordpress.com/2016/08/16/crystal-serenity/

Not only climate change but as a farmer I see ever increasing worldwide crop yields and tree growth being driven by rising CO2 levels especially legumes  eg ..clovers /peas. Positive thought some of this extra CO2 is at least going into extra plant material. Please move  if off topic.

[knocker]

8 hours ago, Northernlights said:

Not only climate change but as a farmer I see ever increasing worldwide crop yields and tree growth being driven by rising CO2 levels especially legumes  eg ..clovers /peas. Positive thought some of this extra CO2 is at least going into extra plant material. Please move  if off topic.

A more detailed look at this (although it is digressing from the point of my original post)

Rising CO2 has ‘greened’ world’s plants and trees

https://www.carbonbrief.org/rising-co2-has-greened-worlds-plants-and-trees

Edited August 17, 2016 by knocker

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Piecing together the Arctic’s sea ice history back to 1850

http://www.skepticalscience.com/news.php?n=3479

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How predictable is the timing of a summer ice-free Arctic?†

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Climate Model simulations give a large range of over 100 years for predictions of when the Arctic could first become ice-free in the summer, and many studies have attempted to narrow this uncertainty range. However, given the chaotic nature of the climate system, what amount of spread in the prediction of an ice-free summer Arctic is inevitable? Based on results from large ensemble simulations with the Community Earth System Model, we show that internal variability alone leads to a prediction uncertainty of about two decades, while scenario uncertainty between the strong (RCP8.5) and medium (RCP4.5) forcing scenarios adds at least another 5 years. Common metrics of the past and present mean sea ice state (such as ice extent, volume, and thickness) as well as global mean temperatures do not allow a reduction of the prediction uncertainty from internal variability.

http://onlinelibrary.wiley.com/doi/10.1002/2016GL070067/abstract

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Early onset of industrial-era warming across the oceans and continents

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The evolution of industrial-era warming across the continents and oceans provides a context for future climate change

and is important for determining climate sensitivity and the processes that control regional warming. Here we use post-

 1500 palaeoclimate records to show that sustained industrial-era warming of the tropical oceans first developed during

the mid-nineteenth century and was nearly synchronous with Northern Hemisphere continental warming. The early

onset of sustained, significant warming in palaeoclimate records and model simulations suggests that greenhouse forcing

of industrial-era warming commenced as early as the mid-nineteenth century and included an enhanced equatorial

ocean response mechanism. The development of Southern Hemisphere warming is delayed in reconstructions, but this

apparent delay is not reproduced in climate simulations. Our findings imply that instrumental records are too short

to comprehensively assess anthropogenic climate change and that, in some regions, about 180 years of industrial-era

warming has already caused surface temperatures to emerge above pre-industrial values, even when taking natural

variability into account.

http://www.nature.com/articles/nature19082.epdf?referrer_access_token=flPZlaDcn64QH3UDfmF8h9RgN0jAjWel9jnR3ZoTv0M-CAOCGNwb4Wu6NFdGGSgFB-Cu3nEDdaUbUxC-kJGtp_q0QNSYvzUPOp4jLViVhLj-w0-eJHSFVRQh0MARgb04x1JRvKrOpKd5pRrIaBQMfnO_hyCY_7yLutaeTD8HG1MhvlQyWx7qOgYR2sFoWTruGepw1BaPl2SC0ZTiPJBMOcww3jE1TD156CH0sdaTlawCAhqBKBWBZxKZb4JPlN1pnqytf9kvHYA5-tzrd14yvw%3D%3D&tracking_referrer=www.abc.net.au

Article

https://www.carbonbrief.org/scientists-clarify-starting-point-for-human-caused-climate-change?utm_so&utm_content=buffer032b5&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Edited August 25, 2016 by knocker

[knocker]

An update on mid-latitude cyclones and climate change

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Why is it so hard to say what the future North European climate will look like? A recent review paper by Shaw et al, 2016 explains the reason in persuasive terms.

The weather over Northern Europe is strongly shaped by low and high barotropic pressure, associated with so-called mid-latitude cyclones. Most people refer to the most extreme cyclones as storms, although meteorologists like to use the term “synoptic storms”. The North European climate may be regarded as the weather statistics for over this region.

Shaw et al. (2016) provide a thorough assessment of the current knowledge about global warming and mid-latitude storms. They argue that there is a “tug of war” between various conditions which will affect the outcome for future mid-latitude storms as well as the jet stream. Such conditions include the south-north temperature gradient, the vertical temperature structure, ocean temperatures, and cloud cover, many of which are difficult to calculate:

http://www.realclimate.org/index.php/archives/2016/09/an-update-on-mid-latitude-cyclones-and-climate-change/