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Found 20 results

  1. Atmospheric Dynamics Feedback: Concept, Simulations, and Climate Implications Authors: Michael P. Byrne and Tapio Schneider First Published: January 12th, 2018 Published on line: March 26th, 2018 Abstract: The regional climate response to radiative forcing is largely controlled by changes in the atmospheric circulation. It has been suggested that global climate sensitivity also depends on the circulation response, an effect called the “atmospheric dynamics feedback.” Using a technique to isolate the influence of changes in atmospheric circulation on top-of-the-atmosphere radiation, the authors calculate the atmospheric dynamics feedback in coupled climate models. Large-scale circulation changes contribute substantially to all-sky and cloud feedbacks in the tropics but are relatively less important at higher latitudes. Globally averaged, the atmospheric dynamics feedback is positive and amplifies the near-surface temperature response to climate change by an average of 8% in simulations with coupled models. A constraint related to the atmospheric mass budget results in the dynamics feedback being small on large scales relative to feedbacks associated with thermodynamic processes. Idealized-forcing simulations suggest that circulation changes at high latitudes are potentially more effective at influencing global temperature than circulation changes at low latitudes, and the implications for past and future climate change are discussed. Link to Paper: https://pdfs.semanticscholar.org/8f29/8a8c3782fc69b576804e2ad9d037daf1df3f.pdf
  2. Response of the Zonal Mean Atmospheric Circulation to El Niño versus Global Warming Authors: Jian Lu, Gang Chen and Dargan M. W. Frierson First Published: March 11th, 2008 Published on line: November 15th, 2008 Abstract: The change in the zonal mean atmospheric circulation under global warming is studied in comparison with the response to El Niño forcing, by examining the model simulations conducted for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In contrast to the strengthening and contraction of the Hadley cell and the equatorward shift of the tropospheric zonal jets in response to El Niño, the Hadley cell weakens and expands poleward, and the jets move poleward in a warmed climate, despite the projected “El Niño–like” enhanced warming over the equatorial central and eastern Pacific. The hydrological impacts of global warming also exhibit distinct patterns over the subtropics and midlatitudes in comparison to the El Niño. Two feasible mechanisms are proposed for the zonal mean circulation response to global warming: 1) The increase in static stability of the subtropical and midlatitude troposphere, a robust result of the quasi-moist adiabatic adjustment to the surface warming, may stabilize the baroclinic eddy growth on the equatorward side of the storm tracks and push the eddy activity and the associated eddy-driven wind and subsidence poleward, leading to the poleward expansion of the Hadley cell and the shift of midlatitude jets; 2) the strengthening of the midlatitude wind at the upper troposphere and lower stratosphere, arguably a consequence of increases in the meridional temperature gradient near the tropopause level due to the tropospheric warming and tropopause slope, may increase the eastward propagation of the eddies emanating from the midlatitudes, and thus the subtropical region of wave breaking displaces poleward together with the eddy-driven circulation. Both mechanisms are somewhat, if not completely, distinct from those in response to the El Niño condition. Link to full paper: https://journals.ametsoc.org/doi/pdf/10.1175/2008JCLI2200.1 Credit goes to Eric @Webberweather for finding this presentation - thank you.
  3. Global Warming and ENSO – A “Helter-Skelter” Atmosphere Authors: Daphne Thompson (for WDT) Published: 11th December, 2017 Abstract: (None but I extracted this from the text): The purpose of this article is to make an effort to illustrate circulation impacts due to climate change, and give some high-level observational evidence of a La Niña-like response due to global warming, including at present. From another perspective, the ongoing El Niño could be contributing to La Niña aspects of the current atmospheric circulation given that it may be amplifying the present increase in the global mean temperature. Emphasis is then placed on the relevancy of climate change to subseasonal forecasting, including the present 16-30 day outlooks issued by WDT. The “global warming-La Niña” connection has been gaining some recognition in a few very recent publications in the refereed literature, as well as in on-line blogs written by well-respected scientists. The reader is encouraged to do a search. No attempt will be made to get into the complicated issues of the causes of climate change (including global warming) other than described above Link to full paper: https://blog.weatherops.com/global-warming-and-enso-a-helter-skelter-atmosphere Credit goes to Tams @Tamara for finding this paper - thank you.
  4. How Global Warming and Arctic Ice Melt Intensify Hurricanes - YouTube Presentation Presented By: Dr Jennifer Francis (Research Professor at Rutgers University's Institute of Marine and Coastal Sciences since 1994) Interviewed By: Greg Wilpert Broadcast Team: The Real News Network Presentation Date: 21st September, 2018 Link to YouTube presentation (13 minutes): You can click on the chart above or use this link: https://www.youtube.com/watch?time_continue=45&v=cZTiFA39T8I
  5. A real-time Global Warming Index Authors: Dr. K. Haustein, M. R. Allen, P. M. Forster, F. E. L. Otto, D. M. Mitchell, H. D. Matthews and D. J. Frame Published: 13th November, 2017 Abstract: We propose a simple real-time index of global human-induced warming and assess its robustness to uncertainties in climate forcing and short-term climate fluctuations. This index provides improved scientific context for temperature stabilisation targets and has the potential to decrease the volatility of climate policy. We quantify uncertainties arising from temperature observations, climate radiative forcings, internal variability and the model response. Our index and the associated rate of human-induced warming is compatible with a range of other more sophisticated methods to estimate the human contribution to observed global temperature change. Link to full paper: https://www.nature.com/articles/s41598-017-14828-5
  6. Projected SSTs over 21st century: Changes in mean, variability & extremes for large marine ecosystem regions of Northern Oceans Authors: Michael A. Alexander (NOAA), James D. Scott, Kevin D. Friedland, Katherine E. Mills, Janet A. Nye, Andrew J. Pershing and Andrew C. Thomas Published: 26th January, 2018 Abstract: Global climate models were used to assess changes in the mean, variability and extreme sea surface temperatures (SSTs) in northern oceans with a focus on large marine ecosystems (LMEs) adjacent to North America, Europe, and the Arctic Ocean. Results were obtained from 26 models in the Community Model Intercomparison Project Phase 5 (CMIP5) archive and 30 simulations from the National Center for Atmospheric Research Large Ensemble Community Project (CESM-LENS). All of the simulations used the observed greenhouse gas concentrations for 1976–2005 and the RCP8.5 “business as usual” scenario for greenhouse gases through the remainder of the 21st century. In general, differences between models are substantially larger than among the simulations in the CESM-LENS, indicating that the SST changes are more strongly affected by model formulation than internal climate variability. The annual SST trends over 1976–2099 in the 18 LMEs examined here are all positive ranging from 0.05 to 0.5°C decade–1. SST changes by the end of the 21st century are primarily due to a positive shift in the mean with only modest changes in the variability in most LMEs, resulting in a substantial increase in warm extremes and decrease in cold extremes. The shift in the mean is so large that in many regions SSTs during 2070–2099 will always be warmer than the warmest year during 1976–2005. The SST trends are generally stronger in summer than in winter, as greenhouse gas heating is integrated over a much shallower climatological mixed layer depth in summer than in winter, which amplifies the seasonal cycle of SST over the 21stcentury. In the Arctic, the mean SST and its variability increases substantially during summer, when it is ice free, but not during winter when a thin layer of ice reforms and SSTs remain near the freezing point. Link to full paper: http://www.readcube.com/articles/10.1525/elementa.191 Link to a presentation of this paper (slides only): http://meetings.pices.int/publications/presentations/2018-Climate-Change/S01-D1-1700-Alexander_no extra slides.pdf
  7. Effect of remote sea surface temperature change on tropical cyclone potential intensity Authors: Gabriel A. Vecchi and Brian J. Soden (Nature volume 450, pages 1066–1070) Published: 13th December, 2007 Abstract: The response of tropical cyclone activity to global warming is widely debated. It is often assumed that warmer sea surface temperatures provide a more favourable environment for the development and intensification of tropical cyclones, but cyclone genesis and intensity are also affected by the vertical thermodynamic properties of the atmosphere. Here we use climate models and observational reconstructions to explore the relationship between changes in sea surface temperature and tropical cyclone ‘potential intensity’—a measure that provides an upper bound on cyclone intensity and can also reflect the likelihood of cyclone development. We find that changes in local sea surface temperature are inadequate for characterizing even the sign of changes in potential intensity, but that long-term changes in potential intensity are closely related to the regional structure of warming; regions that warm more than the tropical average are characterized by increased potential intensity, and vice versa. We use this relationship to reconstruct changes in potential intensity over the twentieth century from observational reconstructions of sea surface temperature. We find that, even though tropical Atlantic sea surface temperatures are currently at a historical high, Atlantic potential intensity probably peaked in the 1930s and 1950s, and recent values are near the historical average. Our results indicate that—per unit local sea surface temperature change—the response of tropical cyclone activity to natural climate variations, which tend to involve localized changes in sea surface temperature, may be larger than the response to the more uniform patterns of greenhouse-gas-induced warming. Link to full paper: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.363.5657&rep=rep1&type=pdf
  8. Bring Back 1962-63

    Causes of Antarctic Change - A Discussion

    Causes of Antarctic Change - A Discussion Workshop Presentation: Aspen Global Change Institute, Aspen, Colorado Workshop Programme: “Understanding the Causes and Consequences of Polar Amplification” - June 12th -16th, 2017 Workshop Discussion: Relating to their presentations (on the same afternoon) Presenters: John C Fyfe, Baek-Min Kim, Lorenzo Polvani, David Schneider, Karen L Smith, Laurent Terray and Xiangdong Zhang Presentation Date: 13th June, 2017 Link to full discussion (27 minute video): https://www.agci.org/lib/17s1/part-iv-discussion-causes-antarctic-change Link to full agenda and presentations: https://www.agci.org/event/17s1
  9. The Response of the Southern Ocean and Antarctic Sea Ice to Freshwater from Ice Shelves in an Earth System Model Authors: Andrew G. Pauling, Cecelia M. Bitz, J. Smith and Patricia J. Langhorne Published: 5th December, 2015 Abstract: The possibility that recent Antarctic sea ice expansion resulted from an increase in freshwater reaching the Southern Ocean is investigated here. The freshwater flux from ice sheet and ice shelf mass imbalance is largely missing in models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). However, on average, precipitation minus evaporation (P − E) reaching the Southern Ocean has increased in CMIP5 models to a present value that is about greater than preindustrial times and 5–22 times larger than estimates of the mass imbalance of Antarctic ice sheets and shelves (119–544 ). Two sets of experiments were conducted from 1980 to 2013 in CESM1(CAM5), one of the CMIP5 models, artificially distributing freshwater either at the ocean surface to mimic iceberg melt or at the ice shelf fronts at depth. An anomalous reduction in vertical advection of heat into the surface mixed layer resulted in sea surface cooling at high southern latitudes and an associated increase in sea ice area. Enhancing the freshwater input by an amount within the range of estimates of the Antarctic mass imbalance did not have any significant effect on either sea ice area magnitude or trend. Freshwater enhancement of raised the total sea ice area by 1 × 106 km2, yet this and even an enhancement of was insufficient to offset the sea ice decline due to anthropogenic forcing for any period of 20 years or longer. Further, the sea ice response was found to be insensitive to the depth of freshwater injection. Link to full paper: https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0501.1
  10. Causes of Arctic Sea Ice Loss - A Discussion Workshop Presentation: Aspen Global Change Institute, Aspen, Colorado Workshop Programme: “Understanding the Causes and Consequences of Polar Amplification” - June 12th -16th, 2017 Workshop Discussion: Relating to their presentations (on the same morning) Presenters: Qinghua Ding, Michael Sigmond and Zachary Michael Labe Presentation Date: 12th June, 2017 Link to full discussion (30 minute video): https://www.agci.org/lib/17s1/discussion Link to full agenda and presentations: https://www.agci.org/event/17s1
  11. Understanding the Causes and Consequences of Polar Amplification Workshops: Aspen Global Change Institute, Aspen, Colorado (mission statement: "We’re dedicated to advancing the understanding of Earth system science and global environmental change through interdisciplinary workshops, research and consulting, and education and outreach") Workshop Dates: June 12th -16th, 2017 Summary: The Arctic is warming twice as fast as the global average temperature. How these rapid changes will affect the Arctic region is critical to understand, though the significance of this understanding extends beyond the region since changes in the Arctic are increasingly understood to interact with the climate system of the Earth as a whole via atmospheric circulation and ocean currents. In particular, as climate change continues understanding how changes in the Arctic will affect weather and climate of the northern continents is a critical and timely question. Improved understanding of the mechanisms of teleconnection in these systems will shed light on how the Earth’s climate system works as it departs further from the norms of the 20th century. The ability to model these changes has the potential to better describe future climate and its ecological and societal impacts as the century unfolds. To make progress, it is imperative to consider the larger context of the causes and consequences of polar amplification in the global climate system, and examine connections between the faster pace of warming in the polar regions compared to lower latitudes. Link to full agenda and presentations: https://www.agci.org/event/17s1 Please note that some of these presentations will appear individually in this portal.
  12. Consistency and discrepancy in the atmospheric response to Arctic sea-ice loss across climate models Authors: James A. Screen, Clara Deser, Doug M. Smith, Xiangdong Zhang, Russell Blackport, Paul J. Kushner, Thomas Oudar, Kelly E. McCusker & Lantao Sun Published: 5th February 2018 Abstract: The decline of Arctic sea ice is an integral part of anthropogenic climate change. Sea-ice loss is already having a significant impact on Arctic communities and ecosystems. Its role as a cause of climate changes outside of the Arctic has also attracted much scientific interest. Evidence is mounting that Arctic sea-ice loss can affect weather and climate throughout the Northern Hemisphere. The remote impacts of Arctic sea-ice loss can only be properly represented using models that simulate interactions among the ocean, sea ice, land and atmosphere. A synthesis of six such experiments with different models shows consistent hemispheric-wide atmospheric warming, strongest in the mid-to-high-latitude lower troposphere; an intensification of the wintertime Aleutian Low and, in most cases, the Siberian High; a weakening of the Icelandic Low; and a reduction in strength and southward shift of the mid-latitude westerly winds in winter. The atmospheric circulation response seems to be sensitive to the magnitude and geographic pattern of sea-ice loss and, in some cases, to the background climate state. However, it is unclear whether current-generation climate models respond too weakly to sea-ice change. We advocate for coordinated experiments that use different models and observational constraints to quantify the climate response to Arctic sea-ice loss. Link to full paper: https://www.agci.org/sites/default/files/pdfs/lib/main/Screen et al. 2018. Consistency and discrepancy in the atmospheric response to Arctic sea-ice loss across climate models.pdf
  13. The remote effect of the Tibetan Plateau on downstream flow in early summer Authors: Yafei Wang, Xiangde Xu, Anthony R. Lupo, Pingyun Li and Zhicong Yin Published: 11th October, 2011 Abstract: By using numerical experiments and observational data, this study examined the uplifting and thermal effects of the Tibetan Plateau (TP) on downstream airflow in early summer. Our principal finding is that the uplifting effect of the TP in an Atmospheric General Climate Model (AGCM), including air made warmer than its surroundings climatologically by the huge topography, results mainly in a local response in the atmosphere, i.e., a large ridge north of the TP in the troposphere in June. There was no Rossby wave response to the uplifting effect. However, simulations and statistical analyses strongly suggested that the anomalous TP atmospheric heating associated with global climate warming tends to excite a Rossby wave originating from the TP via Lake Baikal and continuing to move through the Okhotsk Sea to downstream areas. The appearance of the Rossby wave coincides with the positive phase of the eastern part of a normal stationary wave originating in the Caspian Sea traveling via the Okhotsk Sea to the sea area east of Japan that often occurs in June. Thus the TP atmospheric heating acts as an additional wave source in relaying and enhancing the eastern part of the normal wave propagation. Its path usually lies beyond 40°N latitude, which is where the westerly jet stream takes over the role of waveguide. Link to full paper: https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011JD015979
  14. A Sensitivity Study of the Thermodynamic Environment on GFDL Model Hurricane Intensity: Implications for Global Warming Author: Weixing Shen Published: Jan 2000 Abstract: In this study, the effect of thermodynamic environmental changes on hurricane intensity is extensively investigated with the National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics Laboratory hurricane model for a suite of experiments with different initial upper-tropospheric temperature anomalies up to ±4°C and sea surface temperatures ranging from 26° to 31°C given the same relative humidity profile. The results indicate that stabilization in the environmental atmosphere and sea surface temperature (SST) increase cause opposing effects on hurricane intensity. The offsetting relationship between the effects of atmospheric stability increase (decrease) and SST increase (decrease) is monotonic and systematic in the parameter space. This implies that hurricane intensity increase due to a possible global warming associated with increased CO2 is considerably smaller than that expected from warming of the oceanic waters alone. The results also indicate that the intensity of stronger (weaker) hurricanes is more (less) sensitive to atmospheric stability and SST changes. The model-attained hurricane intensity is found to be well correlated with the maximum surface evaporation and the large-scale environmental convective available potential energy. The model-attained hurricane intensity is highly correlated with the energy available from wet-adiabatic ascent near the eyewall relative to a reference sounding in the undisturbed environment for all the experiments. Coupled hurricane–ocean experiments show that hurricane intensity becomes less sensitive to atmospheric stability and SST changes since the ocean coupling causes larger (smaller) intensity reduction for stronger (weaker) hurricanes. This implies less increase of hurricane intensity related to a possible global warming due to increased CO2. Link to full paper: https://journals.ametsoc.org/doi/full/10.1175/1520-0442(2000)013<0109%3AASSOTT>2.0.CO%3B2
  15. Blessed Weather

    Global Warming and Hurricanes

    Global Warming and Hurricanes Authors: NOAA/GFDL Published: Regularly updated. Last updated April 2018 Abstract: Two frequently asked questions on global warming and hurricanes are the following: Have humans already caused a detectable increase in Atlantic hurricane activity or global tropical cyclone activity? What changes in hurricane activity are expected for the late 21st century, given the pronounced global warming scenarios from IPCC models? In this review, we address these questions in the context of published research findings. We will first present our main conclusions and then follow with some background discussion of the research that leads to these conclusions. “Detectable” change here will refer to a change that is large enough to be clearly distinguishable from the variability due to natural causes. Our main conclusions are: It is premature to conclude that human activities–and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity. Anthropogenic warming by the end of the 21st century will likely cause tropical cyclones globally to be more intense on average (by 2 to 11% according to model projections for an IPCC mid-range scenario). There are better than even odds that anthropogenic warming over the next century will lead to an increase in the occurrence of very intense tropical cyclones globally–an increase that would be substantially larger in percentage terms than the 2-11% increase in the average storm intensity. This increase in intense storm occurrence is projected despite a likely decrease (or little change) in the global numbers of all tropical cyclones. However, there is at present only low confidence that such an increase in very intense storms will occur in the Atlantic basin. Link to full paper: https://www.gfdl.noaa.gov/global-warming-and-hurricanes/ Note: There is also an older May 2008 paper from NOAA/GFDL titled: "Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions" that covers the above topic in more technical detail. Abstract: Increasing sea surface temperatures in the tropical Atlantic Ocean and measures of Atlantic hurricane activity have been reported to be strongly correlated since at least 1950, raising concerns that future greenhouse-gas-induced warming could lead to pronounced increases in hurricane activity. Models that explicitly simulate hurricanes are needed to study the influence of warming ocean temperatures on Atlantichurricane activity, complementing empirical approaches. Our regional climate model of the Atlantic basin reproduces the observed rise in hurricane counts between 1980 and 2006, along with much of the interannual variability, when forced with observed sea surface temperatures and atmospheric conditions Here we assess, in our model system, the changes in large-scale climate that are projected to occur by the end of the twenty-first century by an ensemble of global climate models, and find that Atlantic hurricane and tropical storm frequencies are reduced. At the same time, near-storm rainfall rates increase substantially. Our results do not support the notion of large increasing trends in either tropical storm or hurricane frequency driven by increases in atmospheric greenhouse-gas concentrations. Link to full paper: https://www.gfdl.noaa.gov/wp-content/uploads/files/user_files/gav/publications/ksgvh_08_hurr.pdf
  16. Nonlinear response of mid-latitude weather to the changing Arctic Authors: James E. Overland, , Klaus Dethloff, Jennifer A. Francis, Richard J. Hall, Edward Hanna, Seong-Joong Kim, James A. Screen, Theodore G. Shepherd & Timo Vihma Published: 26th October, 2016 Abstract: Are continuing changes in the Arctic influencing wind patterns and the occurrence of extreme weather events in northern mid-latitudes? The chaotic nature of atmospheric circulation precludes easy answers. The topic is a major science challenge, as continued Arctic temperature increases are an inevitable aspect of anthropogenic climate change. We propose a perspective that rejects simple cause-and-effect pathways and notes diagnostic challenges in interpreting atmospheric dynamics. We present a way forward based on understanding multiple processes that lead to uncertainties in Arctic and mid-latitude weather and climate linkages. We emphasize community coordination for both scientific progress and communication to a broader public. Link to full paper: http://epic.awi.de/41790/1/OVERLAND_nclimate3121.pdf
  17. Effects of Arctic Sea Ice Decline on Weather and Climate: A Review Authors: Timo Vihma Published: 9th March, 2014 Abstract: The areal extent, concentration and thickness of sea ice in the Arctic Ocean and adjacent seas have strongly decreased during the recent decades, but cold, snow-rich winters have been common over mid-latitude land areas since 2005. A review is presented on studies addressing the local and remote effects of the sea ice decline on weather and climate. It is evident that the reduction in sea ice cover has increased the heat flux from the ocean to atmosphere in autumn and early winter. This has locally increased air temperature, moisture, and cloud cover and reduced the static stability in the lower troposphere. Several studies based on observations, atmospheric reanalyses, and model experiments suggest that the sea ice decline, together with increased snow cover in Eurasia, favours circulation patterns resembling the negative phase of the North Atlantic Oscillation and Arctic Oscillation. The suggested large-scale pressure patterns include a high over Eurasia, which favours cold winters in Europe and northeastern Eurasia. A high over the western and a low over the eastern North America have also been suggested, favouring advection of Arctic air masses to North America. Mid-latitude winter weather is, however, affected by several other factors, which generate a large inter-annual variability and often mask the effects of sea ice decline. In addition, the small sample of years with a large sea ice loss makes it difficult to distinguish the effects directly attributable to sea ice conditions. Several studies suggest that, with advancing global warming, cold winters in mid-latitude continents will no longer be common during the second half of the twenty-first century. Recent studies have also suggested causal links between the sea ice decline and summer precipitation in Europe, the Mediterranean, and East Asia. Link to full paper: https://link.springer.com/article/10.1007%2Fs10712-014-9284-0
  18. Warm Arctic episodes linked with increased frequency of extreme winter weather in the United States Authors: Judah Cohen, Karl Pfeiffer & Jennifer A. Francis Published: 13th March, 2013 (Nature Communications) Abstract: Recent boreal winters have exhibited a large-scale seesaw temperature pattern characterized by an unusually warm Arctic and cold continents. Whether there is any physical link between Arctic variability and Northern Hemisphere (NH) extreme weather is an active area of research. Using a recently developed index of severe winter weather, we show that the occurrence of severe winter weather in the United States is significantly related to anomalies in pan-Arctic geopotential heights and temperatures. As the Arctic transitions from a relatively cold state to a warmer one, the frequency of severe winter weather in mid-latitudes increases through the transition. However, this relationship is strongest in the eastern US and mixed to even opposite along the western US. We also show that during mid-winter to late-winter of recent decades, when the Arctic warming trend is greatest and extends into the upper troposphere and lower stratosphere, severe winter weather—including both cold spells and heavy snows—became more frequent in the eastern United States. Link to full paper: https://www.nature.com/articles/s41467-018-02992-9
  19. Assessing recent warming using instrumentally homogeneous sea surface temperature records Authors: Zeke Hausfather, Kevin Cowtan, David C. Clarke, Peter Jacobs, Mark Richardson and Robert Rohde Published: 4th January, 2017 (Science Advances) Abstract: Sea surface temperature (SST) records are subject to potential biases due to changing instrumentation and measurement practices. Significant differences exist between commonly used composite SST reconstructions from the National Oceanic and Atmospheric Administration’s Extended Reconstruction Sea Surface Temperature (ERSST), the Hadley Centre SST data set (HadSST3), and the Japanese Meteorological Agency’s Centennial Observation-Based Estimates of SSTs (COBE-SST) from 2003 to the present. The update from ERSST version 3b to version 4 resulted in an increase in the operational SST trend estimate during the last 19 years from 0.07° to 0.12°C per decade, indicating a higher rate of warming in recent years. We show that ERSST version 4 trends generally agree with largely independent, near-global, and instrumentally homogeneous SST measurements from floating buoys, Argo floats, and radiometer-based satellite measurements that have been developed and deployed during the past two decades. We find a large cooling bias in ERSST version 3b and smaller but significant cooling biases in HadSST3 and COBE-SST from 2003 to the present, with respect to most series examined. These results suggest that reported rates of SST warming in recent years have been underestimated in these three data sets. Link to full paper: http://advances.sciencemag.org/content/advances/3/1/e1601207.full.pdf
  20. Reconstruction of autumn sea ice extent changes since AD1289 in the Barents-Kara Sea, Arctic Authors: Qi Zhang, Cunde Xiao, Minghu Ding and Tingfeng Dou (Science China earth Sciences) Published: 3rd May, 2018 Abstract: Using high-resolution ice core and tree ring proxies for sea ice extent (SIE), we reconstructed a robust time series of autumn SIE over the Barents-Kara (B-K) sector of the Arctic from AD1289–1993. After intercomparing the results and statistical parameters using the ordinary least squares regression (OLSR), the principle component regression (PCR) and the partial least squares regression (PLSR) methods, SIE time series were synthesized into a more robust series using the weighted average method, which used the explained variances as weights. The results showed that from the end of the 13th century to the end of 18th century, the autumn B-K SIE was large, with large variations and a slightly expanding trend overall. This reflected significant multidecadal oscillations under the Little Ice Age (LIA) background. The B-K SIE began to decrease at the end of the 18th century, and a shrinking trend became significant during the second half of the 19th century, which lasted into the 1930s–1940s. The 1930s–1940s was a period with a relatively low SIE in the B-K Sea, and the SIE had a short period of expansion from the 1940s–1970s. However, the B-K SIE has continuously and significantly shrank since the 1970s. The reduction in the B-K SIE since the end of the 18th century has been unprecedented in both duration and speed over the last 700 years. The B-K SIE has retreated significantly since the 1970s, with a speed 6.18 times greater than the former mean retreating speed. The industrial revolution may be a dominant factor in this result. The Arctic SIE in recent years may be the lowest it has been over the last millennium. Link to full paper (only available in Chinese): http://engine.scichina.com/publisher/scp/journal/SSTe/doi/10.1360/N072017-00385?slug=full text Please note that this very recent paper in only available in Chinese. I tried Google translate and much of it is readable but it does not copy easily and becomes a very drawn out document. So, I provided the link above. This appears to be free-to-view but the full English version is behind a very costly paywall. There is, however a preview of the first two pages on this link: Link to Abstract + first two pages (paywall site to full paper in English): https://link.springer.com/article/10.1007%2Fs11430-017-9196-4
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