New Research

[Nouska]

WWOSC conference starts tomorrow. Book of abstracts.

 

http://asp-us.secure-zone.net/v2/index.jsp?id=144/235/1368&lng=en

[mikeworst]

"From research stations drifting on ice floes to high-tech aircraft radar, scientists have been tracking the depth of snow that accumulates on Arctic sea ice for almost a century" Sorry but have to call bsh on that statement.

[Gray-Wolf]

"From research stations drifting on ice floes to high-tech aircraft radar, scientists have been tracking the depth of snow that accumulates on Arctic sea ice for almost a century" Sorry but have to call bsh on that statement.

 

http://onlinelibrary.wiley.com/doi/10.1002/2014JC009985/abstract

 

For me the 'ICEBridge data was an easy confirm with open waters now over the areas that the early ( heaviest?) snows fall over? You don't get much snow depth when it falls into an ocean trying to lose heat before re-freeze?

[mikeworst]

It might be for you but not for thinking folk. The statement is misleading and the results of the study speculative at best . May possibly be valid from circa 2009 but that too is iffy. Nobody disputes that the arctic as opposed to antarctic ice has retreated in recent years.

[knocker]

Natural variability, radiative forcing and climate response in the recent hiatus reconciled

 

Global mean surface warming over the past 15 years or so has been less than in earlier decades and than simulated by most climate models¹. Natural variability^{2, 3, 4}, a reduced radiative forcing^{5, 6, 7}, a smaller warming response to atmospheric carbon dioxide concentrations^{8, 9} and coverage bias in the observations¹⁰ have been identified as potential causes. However, the explanations of the so-called ‘warming hiatus’ remain fragmented and the implications for long-term temperature projections are unclear. Here we estimate the contribution of internal variability associated with the El Niño/Southern Oscillation (ENSO) using segments of unforced climate model control simulations that match the observed climate variability. We find that ENSO variability analogous to that between 1997 or 1998 and 2012 leads to a cooling trend of about −0.06 °C. In addition, updated solar and stratospheric aerosol forcings from observations explain a cooling trend of similar magnitude (−0.07 °C). Accounting for these adjusted trends we show that a climate model of reduced complexity with a transient climate response of about 1.8 °C is consistent with the temperature record of the past 15 years, as is the ensemble mean of the models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We conclude that there is little evidence for a systematic overestimation of the temperature response to increasing atmospheric CO₂ concentrations in the CMIP5 ensemble.

 

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2228.html?utm_content=bufferdcac2&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

[knocker]

Ocean warming could drive heavy rain bands toward the poles

 

In a world warmed by rising atmospheric greenhouse gas concentrations, precipitation patterns are going to change because of two factors: one, warmer air can hold more water; and two, changing atmospheric circulation patterns will shift where rain falls. According to previous model research, mid- to high-latitude precipitation is expected to increase by as much as 50%. Yet the reasons why models predict this are hard to tease out.

Using a series of highly idealized model runs, Lu et al. found that ocean warming should cause atmospheric precipitation bands to shift toward the poles. The changes in atmospheric circulation brought on by a warming ocean should cause an increase in the intensity and frequency of extreme precipitation events at mid- and high-latitudes, and a reduction in the same near the equator. The changes would mean that, for high-latitude regions, now-rare storms would become much more common.

The authors tested the effect of ocean warming on atmospheric circulation and precipitation using a highly idealized “aquaplanet†model, a representation of the Earth that was just sea and sky, but no land. They ran the model at a range of spatial resolutions and found that the changes in precipitation that stem from changing circulation patterns may possibly outweigh changes that derive from other factors.

 

http://eu.wiley.com/WileyCDA/PressRelease/pressReleaseId-111523.html

[knocker]

Sun's activity influences natural climate change

 

For the first time, a research team has been able to reconstruct the solar activity at the end of the last ice age, around 20,000-10,000 years ago, by analysing trace elements in ice cores in Greenland and cave formations from China. During the last glacial maximum, Sweden was covered in a thick ice sheet that stretched all the way down to northern Germany and sea levels were more than 100 metres lower than they are today, because the water was frozen in the extensive ice caps. The new study shows that the sun's variation influences the climate in a similar way regardless of whether the climate is extreme, as during the Ice Age, or as it is today.Read more at: http://phys.org/news/2014-08-sun-natural-climate.html#jCp

[knocker]

The impact of the permafrost carbon feedback on global climate

 

Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon dioxide (CO₂) and methane (CH₄) to influence global climate. The permafrost carbon feedback (PCF) is the amplification of surface warming due to CO₂ and CH₄ emissions from thawing permafrost. An analysis of available estimates PCF strength and timing indicate 120 Â± 85 Gt of carbon emissions from thawing permafrost by 2100. This is equivalent to 5.7 Â± 4.0% of total anthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 8.5 scenario and would increase global temperatures by 0.29 Â± 0.21 °C or 7.8 Â± 5.7%. For RCP4.5, the scenario closest to the 2 °C warming target for the climate change treaty, the range of cumulative emissions in 2100 from thawing permafrost decreases to between 27 and 100 Gt C with temperature increases between 0.05 and 0.15 °C, but the relative fraction of permafrost to total emissions increases to between 3% and 11%. Any substantial warming results in a committed, long-term carbon release from thawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting for permafrost emissions risks overshooting the 2 °C warming target. Climate projections in the IPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do not adequately account for emissions from thawing permafrost and the effects of the PCF on global climate. We recommend the IPCC commission a special assessment focusing on the PCF and its impact on global climate to supplement the AR5 in support of treaty negotiation.

 

http://iopscience.iop.org/1748-9326/9/8/085003/pdf/1748-9326_9_8_085003.pdf

[knocker]

Has the puzzle of rapid climate change in the last ice age been solved? New report published in Nature shows that small variations in the climate system can result in dramatic temperature changes

 

Bremerhaven, Germany, August 19th, 2014.  Over the past one hundred thousand years cold temperatures largely prevailed over the planet in what is known as the last ice age. However, the cold period was repeatedly interrupted by much warmer climate conditions. Scientists have long attempted to find out why these drastic temperature jumps of up to ten degrees took place in the far northern latitudes within just a few decades. Now, for the first time, a group of researchers at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have been able to reconstruct these climate changes during the last ice age using a series of model simulations. The surprising finding is that minor variations in the ice sheet size can be sufficient to trigger abrupt climate changes. The new study was published online in the scientific journal Nature last week and will be appearing in the 21 August print issue.

 

http://www.awi.de/en/news/press_releases/detail/item/has_the_puzzle_of_rapid_climate_change_in_the_last_ice_age_been_solved_new_report_published_in_natu/?tx_list_pi1[mode]=6&cHash=ebf20a9866cdab63f8180f9a9e9b148a

[knocker]

Record decline of ice sheets: For the first time scientists map elevation changes of Greenlandic and Antarctic glaciers

 

Bremerhaven, 20^th August 2014. Researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have for the first time extensively mapped Greenland’s and Antarctica’s ice sheets with the help of the ESA satellite CryoSat-2 and have thus been able to prove that the ice crusts of both regions momentarily decline at an unprecedented rate. In total the ice sheets are losing around 500 cubic kilometres of ice per year. This ice mass corresponds to a layer that is about 600 metres thick and would stretch out over the entire metropolitan area of Hamburg, Germany's second largest city. The maps and results of this study are published today in The Cryosphere, an open access journal of the European Geosciences Union (EGU).

 

http://www.awi.de/en/news/press_releases/detail/item/record_decline_of_ice_sheets_for_the_first_time_scientists_map_elevation_changes_of_greenlandic_and/?cHash=40fbf2d15cbc909996cc02458d8cd973

[knocker]

New study on climate history: Arctic sea ice influenced force of the Gulf Stream

 

Bremerhaven, 15 August 2014. The force of the Gulf Stream was significantly influenced by the sea ice situation in the Fram Strait in the past 30,000 years. Scientists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) come to this conclusion in a new study that appears today in the journal Earth and Planetary Science Letters. On the basis of biomarkers in deposits on the seafloor, the geologists involved managed for the first time to reconstruct when and how the marine region between Greenland and Svalbard was covered with ice in the past and in what way the Gulf Stream reacted when the sea ice cover suddenly broke up. They concluded that when large amounts of Arctic ice drifted through the Fram Strait to the North Atlantic, the heat transport of the Gulf Stream declined noticeably.

 

http://www.awi.de/en/news/press_releases/detail/item/fram_strait_sea_ice_conditions_triggered_the_power_of_the_gulf_stream/?cHash=c7d3997d3cc7325ef7aa10bbb4e490e7

[knocker]

Ozone-Depleting Compound Persists, NASA Research Shows

 

 

 

http://www.nasa.gov/press/2014/august/ozone-depleting-compound-persists-nasa-research-shows/index.html#.U_YyIKOz1X4

[Polar Maritime]

Yes more here Knock.. http://www.nasa.gov/press/2014/august/ozone-depleting-compound-persists-nasa-research-shows/index.html#.U_byDvldXfJ

[knocker]

I suspect I've posted this previously.

 

 

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing

 

Abstract

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around ‘climate response functions’ (CRFs), i.e. the response of the climate to ‘step’ changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate.

 

http://rsta.royalsocietypublishing.org/content/372/2019/20130040

 

A synopsis.

 

http://phys.org/news/2014-08-ocean-circulation-arctic-affected-global.html

Edited August 26, 2014 by knocker

[Polar Maritime]

Extreme Weather is Linked to Global Warming, a New Study Suggests

 

Extreme weather is becoming much more common. Heat waves and heavy rains are escalating, food crops are being damaged, human beings are being displaced due to flooding and animals are migrating toward the poles or going extinct.

Although it has been postulated that these extreme weather events may be due to climate change, a new study has found much better evidence.

 

The research shows blocking patterns — high-pressure systems that become immobile for days or even weeks, causing extreme heat waves and torrential rain — may have doubled in summers over the last decade.

“Since 2000, we have seen a cluster of these events,†lead author Dim Doumou told The Gaurdian earlier this month. “When these high-altitude waves become quasi-stationary, then we see more extreme weather at the surface. It is especially noticeable for heat extremes.â€

It was a blocking pattern that led to the heat wave in Alaska in 2013, and to the devastating floods in Colorado last summer. http://www.universetoday.com/114076/extreme-weather-is-linked-to-global-warming-a-new-study-suggests/

[knocker]

I wonder whether Willard might be interested?

 

Deglacial ice sheet meltdown: orbital pacemaking and CO₂ effects

 

Abstract. One hundred thousand years of ice sheet buildup came to a rapid end ∼25–10 thousand years before present (ka BP), when ice sheets receded quickly and multi-proxy reconstructed global mean surface temperatures rose by ∼3–5 °C. It still remains unresolved whether insolation changes due to variations of earth's tilt and orbit were sufficient to terminate glacial conditions. Using a coupled three-dimensional climate–ice sheet model, we simulate the climate and Northern Hemisphere ice sheet evolution from 78 ka BP to 0 ka BP in good agreement with sea level and ice topography reconstructions. Based on this simulation and a series of deglacial sensitivity experiments with individually varying orbital parameters and prescribed CO₂, we find that enhanced calving led to a slowdown of ice sheet growth as early as ∼8 ka prior to the Last Glacial Maximum (LGM). The glacial termination was then initiated by enhanced ablation due to increasing obliquity and precession, in agreement with the Milankovitch theory. However, our results also support the notion that the ∼100 ppmv rise of atmospheric CO₂ after ∼18 ka BP was a key contributor to the deglaciation. Without it, the present-day ice volume would be comparable to that of the LGM and global mean temperatures would be about 3 °C lower than today. We further demonstrate that neither orbital forcing nor rising CO₂ concentrations alone were sufficient to complete the deglaciation.

 

http://www.clim-past.net/10/1567/2014/cp-10-1567-2014.pdf

Edited August 28, 2014 by knocker

[knocker]

Clarifying the Roles of Greenhouse Gases and ENSO in Recent Global Warming through Their Prediction Performance

 

Abstract

It is well known that natural external forcings and decadal to millennial variability drove changes in the climate system throughout the Holocene. Regarding recent times, attribution studies have shown that greenhouse gases (GHGs) determined the trend of temperature (T) in the last half century, while circulation patterns contributed to modify its inter-annual, decadal or multi-decadal behavior over this period. Here temperature predictions based on vector autoregressive models (VARs) have been used to study the influence of GHGs and El Niño Southern Oscillation (ENSO) on recent temperature behavior. We find that in the last decades of steep temperature increase, ENSO shows just a very short-range influence on T, while GHGs are dominant for each forecast horizon. Conversely and quite surprisingly, in the previous quasi-stationary period the influences of GHGs and ENSO are comparable, even at longer range. Therefore, if the recent hiatus in global temperatures should persist into the near future, we can expect an enhancement of the role of ENSO. Finally, the predictive ability of GHGs is more evident in the Southern hemisphere, where the temperature series is smoother.

 

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00784.1?utm_content=buffera2528&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

[knocker]

New research – August 2014

http://agwobserver.wordpress.com/2014/08/30/new-research-august-2014/

[knocker]

A probabilistic analysis of human influence on recent record global mean temperature changes

 

Abstract

December 2013 was the 346th consecutive month where global land and ocean average surface temperature exceeded the 20th century monthly average, with February 1985 the last time mean temperature fell below this value. Even given these and other extraordinary statistics, public acceptance of human induced climate change and confidence in the supporting science has declined since 2007. The degree of uncertainty as to whether observed climate changes are due to human activity or are part of natural systems fluctuations remains a major stumbling block to effective adaptation action and risk management. Previous approaches to attribute change include qualitative expert-assessment approaches such as used in IPCC reports and use of ‘fingerprinting’ methods based on global climate models. Here we develop an alternative approach which provides a rigorous probabilistic statistical assessment of the link between observed climate changes and human activities in a way that can inform formal climate risk assessment. We construct and validate a time series model of anomalous global temperatures to June 2010, using rates of greenhouse gas (GHG) emissions, as well as other causal factors including solar radiation, volcanic forcing and the El Niño Southern Oscillation. When the effect of GHGs is removed, bootstrap simulation of the model reveals that there is less than a one in one hundred thousand chance of observing an unbroken sequence of 304 months (our analysis extends to June 2010) with mean surface temperature exceeding the 20th century average. We also show that one would expect a far greater number of short periods of falling global temperatures (as observed since 1998) if climate change was not occurring. This approach to assessing probabilities of human influence on global temperature could be transferred to other climate variables and extremes allowing enhanced formal risk assessment of climate change.

 

http://www.sciencedirect.com/science/article/pii/S2212096314000163

[knocker]

An Anatomy of the Cooling of the North Atlantic Ocean in the 1960s and 1970s.

 

Abstract

In the 1960s and early 1970s sea surface temperatures in the North Atlantic Ocean cooled rapidly. There is still considerable uncertainty about the causes of this event, although various mechanisms have been proposed. In this observational study it is demonstrated that the cooling proceeded in several distinct stages. Cool anomalies initially appeared in the mid-1960s in the Nordic Seas and Gulf Stream Extension, before spreading to cover most of the Subpolar Gyre. Subsequently, cool anomalies spread into the tropical North Atlantic before retreating, in the late 1970s, back to the Subpolar Gyre. There is strong evidence that changes in atmospheric circulation, linked to a southward shift of the Atlantic ITCZ, played an important role in the event, particularly in the period 1972-76. Theories for the cooling event must account for its distinctive space-time evolution. Our analysis suggests that the most likely drivers were: 1) The “Great Salinity Anomaly†of the late 1960s; 2) An earlier warming of the subpolar North Atlantic, which may have led to a slow-down in the Atlantic Meridional Overturning Circulation; 3) An increase in anthropogenic sulphur dioxide emissions. Determining the relative importance of these factors is a key area for future work.

 

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00301.1

[knocker]

From 2011 but not sure whether it's been posted before.

 

Adding an interesting article about arctic sea ice during the Holocene Optimum.

[knocker]

Recent seasonal asymmetric changes in the NAO (a marked summer decline and increased winter variability) and associated changes in the AO and Greenland Blocking Index

 

ABSTRACT

Recent changes are found in the means and variability of the North Atlantic Oscillation (NAO) index. There has been a sustained significant recent decrease in the summer NAO since the 1990s and, at the same time, a striking increase in variability of the winter â€“ especially December â€“ NAO that resulted in three of five (two of five) record high (record low) NAO Decembers occurring during 2004–2013 in the 115-year record. These NAO changes are related to an increasing trend in the Greenland Blocking Index (GBI, high pressure over Greenland) in summer and a more variable GBI in December. The enhanced early winter NAO variability originates mainly at the southern node of the NAO but is also related to the more variable GBI in December. Transition seasons (spring and autumn) have remained relatively unchanged over the last 30 years. These results are corroborated using several NAO indices. The Arctic Oscillation (AO) index, although strongly correlated with the NAO, does not show the recent sustained significant summer decrease, but it does show enhanced early winter variability. These recent observed changes are not present in the current generation of global climate models, although the latest process studies do offer insight into their causes. We invoke several plausible climate forcings and feedbacks to explain the recent NAO changes.

 

Press release

 

Winter is coming: British weather set to become more unsettled

http://www.sheffield.ac.uk/news/nr/winter-is-coming-more-unsettled-weather-1.401883

[knocker]

Regime transition of the North Atlantic Oscillation and the extreme cold event over Europe in January-February 2012

 

In this paper, large-scale aspects for the onset of the extreme cold European weather event in January-February 2012 are investigated. It is shown that the outbreak of this extreme cold weather event may be attributed to the transition from a positive North Atlantic Oscillation (NAO⁺ ) event to a long-lasting blocking event over the eastern Atlantic and western Europe (ENAO^− hereafter). A persistent decline of the surface air temperature (SAT) is seen over all of Europe during the long-lived ENAO^− event, while the main region of enhanced precipitation is located over southern Europe and part of central Europe, in association with the presence of a persistent double storm track: one over the Norwegian and Barents Seas and the other over southern Europe.

The NAO⁺ to NAO^− transition events are divided into NAO⁺ to ENAO^− and NAO⁺ to WNAO^− transition events (ENAO^− (WNAO^−) events correspond to eastward- (westward-) displaced NAO^− events whose positive center is defined to be located to the east (west) of 10°W), and a statistical analysis of the NAO⁺ to ENAO^− transition events during 1978-2012 is performed. It is found that there has been a marked increase in the frequency of the NAO⁺ to ENAO^− transition events during the period 2005-2012. Composites of SAT anomalies indicate that the marked decline of the SAT observed over much of Europe is primarily associated with NAO⁺ to ENAO^− transition events. Thus, NAO⁺ to ENAO^− transition events may be more favorable for the extreme cold events over Europe observed in recent winters than other types of NAO^− events.

 

http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-13-00234.1?utm_content=buffer47069&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

[knocker]

Last decade's slow-down in global warming enhanced by an unusual climate anomaly

 

A hiatus in global warming ongoing since 2001 is due to a combination of a natural cooling phase, known as multidecadal variability (MDV) and a downturn of the secular warming trend. The exact causes of the latter, unique in the entire observational record going back to 1850, are still to be identified, according to a JRC article which analysed the phenomena.

 

https://ec.europa.eu/jrc/en/news/climate-anomaly-causes-global-warming-slow-down

[knocker]

A pathway connecting the monsoonal heating to the rapid Arctic ice melt

 

This study provides a monsoonal link to the rapid Arctic ice melt. Each year the planetary scale African Asian monsoonal outflow near the tropopause carries a large anticyclonic gyre that has a longitudinal spread which occupies nearly half of the entire tropics. In recent years, the south Asian summer monsoon has experienced increased rainfall over the northwest of India and Pakistan and it has also contributed to more intense local anticyclonic outflows from this region. The western lobes of these intense upper high pressure areas carry outflows with large heat fluxes from the monsoon belt towards central Asia and eventually to the region of the rapid ice melt of the Canadian Arctic. In this study this spectacular pathway has been defined from air flow trajectories, heat content and heat flux anomalies. Most of these show slow increasing trends in the last 20 years. The monsoonal connection to the rapid Arctic ice melt is a new contribution of this study. This is shown from the passage of a vertical column of large positive values of the heat content anomaly that can be traced from the Asian monsoon belt to the Canadian Arctic. The heat flux along these episodic and intermittently active pathways is shown to be considerably larger than the atmospheric poleward flux across latitude circles and from the oceans. This study contrasts these thermodynamic wave trains (defining this pathway) for the more conventional dynamic wave trains.

 

http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-14-0004.1?utm_content=buffer08325&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer