New Research

[knocker]

 

 

Exceptional twentieth-century slowdown in Atlantic Ocean over turning circulation

 

 

Possible changes in Atlantic meridional overturning circulation (AMOC) provide a key source of uncertainty regarding future

climate change. Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern

Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over

the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered. This time evolution

is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference,

by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland

Ice Sheet to the slowdown. Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC

weakness after 1975 is an unprecedented event in the past millennium (p> 0.99). Further melting of Greenland in the coming

decades could contribute to further weakening of the AMOC.

 

http://www.nature.com/articles/nclimate2554.epdf?referrer_access_token=MVxvuUT8GEjHovuxDcIVDdRgN0jAjWel9jnR3ZoTv0NAhBvJD3qQKAFJ5ZYnRB2DfVKqstvbeSrKxpKUhj2SxF7BcI_loegLGlYCV27ok_Njli4FpCNFd520NkNH-gNy_R7BHOTlk8WVlOM-EydqJ_fXB_3x-E3hIshOeW5WWHqcaPgYVH6Ha2paJACMrQS0vL1bzMOuRrJUW7F2fIb6zTOfarfleGahqDJs4nRADLaiLU5g6rQIKxir0Igbm9o6CWHumkVB6-NveR4QQcF04yFUDA2eESQkZFHTbg4BEjKBHXhfaqQGs3pynjaPS2xr3OFrcGgtAslw6mlPCY2pJBOlEUK_YsjENr2KkPIeQBQ7FzzPlGXxNcMiC-v59Pxv&tracking_referrer=www.washingtonpost.com

 

Discussed here

 

http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/

Edited March 23, 2015 by knocker

[knocker]

I haven't read this as yet

 

 How does the above tie into the Dima and Lohman (2010)

 

Evidence for Two Distinct Modes of Large-Scale Ocean Circulation Changes over the Last Century

 

http://journals.ametsoc.org/doi/pdf/10.1175/2009JCLI2867.1

Edited March 23, 2015 by knocker

[Nouska]

This is a look at the results from the 26 degrees north array which was installed in 2004.

 

http://www.ocean-sci.net/10/29/2014/os-10-29-2014.pdf

 

Observations of the decline do not tally with what the models predicted but very short timescale under consideration.

 

Seems to be a rash of new research on this subject with cryptic statements from the European research organisations about what the models show.

 

Some other links.

 

http://www.reportingclimatescience.com/news-stories/article/north-atlantic-set-to-cool-slightly-says-research.html

 

http://www.exeter.ac.uk/news/featurednews/title_425319_en.html

 

https://www.reading.ac.uk/news-and-events/releases/PR559097.aspx

[knocker]

Oh the irony!

 

One satellite data set is underestimating global warming

 

A new study suggests that the University of Alabama at Huntsville is lowballing the warming of the atmosphere

 

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/mar/25/one-satellite-data-set-is-underestimating-global-warming?CMP=share_btn_tw

Edited March 25, 2015 by knocker

[BornFromTheVoid]

Oh the irony!

 

One satellite data set is underestimating global warming

 

A new study suggests that the University of Alabama at Huntsville is lowballing the warming of the atmosphere

 

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/mar/25/one-satellite-data-set-is-underestimating-global-warming?CMP=share_btn_tw

 

Just to be clear, it isn't actually about trends in surface air or lower troposphere temperatures, but in the tropical mid troposphere (TMT). They find UAH (which shows a larger surface warming trend than other satellite methods) to be the only satellite data set not showing a warming TMT trend , mainly due to errors in how they handle the diurnal drift bias.

This may have implications with regard to the missing tropical tropospheric hotspot that "AGW sceptics" often fall back on, but I'll have to read up on it a bit more.

[keithlucky]

 

 

 

Exceptional twentieth-century slowdown in Atlantic Ocean over turning circulation

 

 

http://www.nature.com/articles/nclimate2554.epdf?referrer_access_token=MVxvuUT8GEjHovuxDcIVDdRgN0jAjWel9jnR3ZoTv0NAhBvJD3qQKAFJ5ZYnRB2DfVKqstvbeSrKxpKUhj2SxF7BcI_loegLGlYCV27ok_Njli4FpCNFd520NkNH-gNy_R7BHOTlk8WVlOM-EydqJ_fXB_3x-E3hIshOeW5WWHqcaPgYVH6Ha2paJACMrQS0vL1bzMOuRrJUW7F2fIb6zTOfarfleGahqDJs4nRADLaiLU5g6rQIKxir0Igbm9o6CWHumkVB6-NveR4QQcF04yFUDA2eESQkZFHTbg4BEjKBHXhfaqQGs3pynjaPS2xr3OFrcGgtAslw6mlPCY2pJBOlEUK_YsjENr2KkPIeQBQ7FzzPlGXxNcMiC-v59Pxv&tracking_referrer=www.washingtonpost.com

 

Discussed here

 

http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/

 

NASA refutes that, in fact that circulation has sped up slightly http://www.nasa.gov/topics/earth/features/atlantic20100325.html

[knocker]

NASA refutes that, in fact that circulation has sped up slightly http://www.nasa.gov/topics/earth/features/atlantic20100325.html

 

NASA refutes what exactly?. Just note the title of the Rahmstorf paper. Rahmstorf, et, al actually cite the study that you will note was 2010 and the study itself supports the Rahmstorf study. I trust you haven't been reading our old friend Anthony again. Over to hopwhopper.

 

 

In fact, this lends support for the Rahmstorf study, which also found that there was a recovery post-1990. Here is a chart of the "AMOC index" from Rahmstorf15 (click to enlarge):

 

http://blog.hotwhopper.com/2015/03/slowing-ocean-circulation-prompts-more.html#more

Edited March 26, 2015 by knocker

[knocker]

Anthropogenic warming has increased drought risk in California

 

California is currently in the midst of a record-setting drought. The drought began in 2012 and now includes the lowest calendar-year

and 12-mo precipitation, the highest annual temperature, and the most extreme drought indicators on record. The extremely warm

and dry conditions have led to acute water shortages, groundwater overdraft, critically low stream flow, and enhanced wild firerisk. Analyzing historical climate observations from California, we find that precipitation deficits in California were more than twice as likely to yield drought years if they occurred when conditions were warm. We find that although there has not been a substantial change in the probability of either negative or moderately negative precipitation anomalies in recent decades, the occurrence of drought years has been greater in the past two decades than in the preceding century. In addition, the probability that precipitation deficits co-occur with warm conditions and the probability that precipitation deficits produce drought have both increased. Climate model experiments with and without anthropogenic forcings reveal that human activities have increased the probability that dry precipitation years are also warm. Further, a large ensemble of climate model realizations reveals that additional global warming over the next few decades is very likely tocreate100% probability that any annual-scale dry period is also extremely warm. We therefore conclude that anthropogenic warming is increasing the probability of co-occurring warm–dry conditions like those that have created the acute human and ecosystem impacts associated with the "exceptional†2012–2014 drought in California

 

http://www.pnas.org/content/early/2015/02/23/1422385112.full.pdf

 

Article

 

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/mar/30/global-warming-and-drought-turning-golden-state-brown

Edited March 30, 2015 by knocker

[knocker]

Mechanisms for low-frequency variability of summer Arctic sea ice extent

 

Satellite observations reveal a substantial decline in September Arctic sea ice extent since 1979, which has played a leading role in the observed recent Arctic surface warming and has often been attributed, in large part, to the increase in greenhouse gases. However, the most rapid decline occurred during the recent global warming hiatus period. Previous studies are often focused on a single mechanism for changes and variations of summer Arctic sea ice extent, and many are based on short observational records. The key players for summer Arctic sea ice extent variability at multidecadal/centennial time scales and their contributions to the observed summer Arctic sea ice decline are not well understood. Here a multiple regression model is developed for the first time, to the author’s knowledge, to provide a framework to quantify the contributions of three key predictors (Atlantic/Pacific heat transport into the Arctic, and Arctic Dipole) to the internal low-frequency variability of Summer Arctic sea ice extent, using a 3,600-y-long control climate model simulation. The results suggest that changes in these key predictors could have contributed substantially to the observed summer Arctic sea ice decline. If the ocean heat transport into the Arctic were to weaken in the near future due to internal variability, there might be a hiatus in the decline of September Arctic sea ice. The modeling results also suggest that at multidecadal/centennial time scales, variations in the atmosphere heat transport across the Arctic Circle are forced by anticorrelated variations in the Atlantic heat transport into the Arctic.

 

http://www.pnas.org/content/early/2015/03/24/1422296112

 

Discussion

 

http://www.carbonbrief.org/blog/2015/03/natural-variability-could-slow-the-pace-of-arctic-summer-sea-ice-loss-study-says/?utm_source=Daily+Carbon+Briefing&utm_campaign=64e4bf4116-cb_daily&utm_medium=email&utm_term=0_876aab4fd7-64e4bf4116-303447709

[knocker]

Scientists predict gradual, prolonged permafrost greenhouse gas emissions

 

A new scientific synthesis suggests a gradual, prolonged release of greenhouse gases from permafrost soils in Arctic and sub-Arctic regions, which may afford society more time to adapt to environmental changes, say scientists in an April 9 paper published in Nature.

 

http://www.eurekalert.org/pub_releases/2015-04/uoaf-spg040715.php?utm_source=twitterfeed&utm_medium=twitter&utm_campaign=Feed%3A+Cryonews+%28CryoNews%29

[knocker]

Ocean acidification and the Permo-Triassic mass extinction

 

Ocean acidification triggered by Siberian Trap volcanism was a possible kill mechanism for the Permo-Triassic Boundary mass extinction, but direct evidence for an acidification event is lacking. We present a high-resolution seawater pH record across this interval, using boron isotope data combined with a quantitative modeling approach. In the latest Permian, increased ocean alkalinity primed the Earth system with a low level of atmospheric CO₂ and a high ocean buffering capacity. The first phase of extinction was coincident with a slow injection of carbon into the atmosphere, and ocean pH remained stable. During the second extinction pulse, however, a rapid and large injection of carbon caused an abrupt acidification event that drove the preferential loss of heavily calcified marine biota.

 

http://www.sciencemag.org/content/348/6231/229

 

Article

 

http://phys.org/news/2015-04-greatest-mass-extinction-driven-acidic.html

[knocker]

Strong influence of westerly wind bursts on El Niño diversity

 

Despite the tremendous progress in the theory, observation and prediction of El Niño over the past three decades, the classification of El Niño diversity and the genesis of such diversity are still debated. This uncertainty renders El Niño prediction a continuously challenging task, as manifested by the absence of the large warm event in 2014 that was expected by many. We propose a unified perspective on El Niño diversity as well as its causes, and support our view with a fuzzy clustering analysis and model experiments. Specifically, the interannual variability of sea surface temperatures in the tropical Pacific Ocean can generally be classified into three warm patterns and one cold pattern, which together constitute a canonical cycle of El Niño/La Niña and its different flavours. Although the genesis of the canonical cycle can be readily explained by classic theories, we suggest that the asymmetry, irregularity and extremes of El Niño result from westerly wind bursts, a type of state-dependent atmospheric perturbation in the equatorial Pacific. Westerly wind bursts strongly affect El Niño but not La Niña because of their unidirectional nature. We conclude that properly accounting for the interplay between the canonical cycle and westerly wind bursts may improve El Niño prediction.

 

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2399.html

 

Article

 

An Improved Classification And Explanation For El Nino (New Research)

[knocker]

Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise

 

The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20^th century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario’s forced signal, but is likely inconsistent with the steepest emission scenario’s forced signal.

 

http://www.nature.com/srep/2015/150421/srep09957/full/srep09957.html

 

Discussion

 

http://phys.org/news/2015-04-global-moderate-empirical.html

Edited April 21, 2015 by knocker

[knocker]

Climate variability and relationships between top-of-atmosphere radiation and temperatures on Earth

 

The monthly global and regional variability in Earth's radiation balance is examined using correlations and regressions between atmospheric temperatures and water vapor with top-of-atmosphere outgoing longwave (OLR), absorbed shortwave (ASR) and net radiation (R_T=ASR-OLR). Anomalous global mean monthly variability in the net radiation is surprisingly large, often more than ±1 W m^−2, and arises mainly from clouds and transient weather systems. Relationships are strongest and positive between OLR and temperatures, especially over land for tropospheric temperatures, except in the deep tropics where high sea surface temperatures are associated with deep convection, high cold cloud-tops and thus less OLR but also less ASR. Tropospheric vertically-averaged temperatures (surface-150 hPa) are thus negatively correlated globally with net radiation (−0.57), implying 2.18±0.10 W m^−2 extra net radiation to space for 1°C increase in temperature. Water vapor is positively correlated with tropospheric temperatures and thus also negatively correlated with net radiation, however when the temperature dependency of water vapor is statistically removed, a significant positive feedback between water vapor and net radiation is revealed globally with 0.87 W m^−2 less OLR to space per mm of total-column water vapor. The regression coefficient between global R_T and tropospheric temperature becomes −2.98 W m^−2K^−1 if water vapor effects are removed, slightly less than expected from black-body radiation (−3.2 W m^−2K^−1), suggesting a positive feedback from clouds and other processes. Robust regional structures provide additional physical insights. The observational record is too short, weather noise too great and forcing too small to make reliable estimates of climate sensitivity.

 

http://onlinelibrary.wiley.com/doi/10.1002/2014JD022887/full

 

Article

 

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/apr/23/changes-in-water-vapor-and-clouds-are-amplifying-global-warming

[knocker]

Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise

 

http://www.nature.com/srep/2015/150421/srep09957/full/srep09957.html

 

Discussion

 

http://phys.org/news/2015-04-global-moderate-empirical.html

 

More discussion on this

 

http://scienceblogs.com/gregladen/2015/04/24/comparing-models-and-empirical-estimates-of-noise-in-the-climate-system/

[knocker]

Warming climate may release vast amounts of carbon from long-frozen Arctic soils

 

Savannah, Ga. - While climatologists are carefully watching carbon dioxide levels in the atmosphere, another group of scientists is exploring a massive storehouse of carbon that has the potential to significantly affect the climate change picture.

University of Georgia Skidaway Institute of Oceanography researcher Aron Stubbins is part of a team investigating how ancient carbon, locked away in Arctic permafrost for thousands of years, is now being transformed into carbon dioxide and released into the atmosphere. The results of the study were published in Geophysical Research Letters.

 

http://news.uga.edu/releases/article/warming-climate-vast-amounts-of-carbon-from-long-frozen-arctic-soils-0415/

[knocker]

Anthropogenic contribution to global occurrence of heavy-precipitation and high-temperature extremes

 

Climate change includes not only changes in mean climate but also in weather extremes. For a few prominent heatwaves and heavy precipitation events a human contribution to their occurrence has been demonstrated^{1, 2, 3, 4, 5}. Here we apply a similar framework but estimate what fraction of all globally occurring heavy precipitation and hot extremes is attributable to warming. We show that at the present-day warming of 0.85 °C about 18% of the moderate daily precipitation extremes over land are attributable to the observed temperature increase since pre-industrial times, which in turn primarily results from human influence⁶. For 2 °C of warming the fraction of precipitation extremes attributable to human influence rises to about 40%. Likewise, today about 75% of the moderate daily hot extremes over land are attributable to warming. It is the most rare and extreme events for which the largest fraction is anthropogenic, and that contribution increases nonlinearly with further warming. The approach introduced here is robust owing to its global perspective, less sensitive to model biases than alternative methods and informative for mitigation policy, and thereby complementary to single-event attribution. Combined with information on vulnerability and exposure, it serves as a scientific basis for assessment of global risk from extreme weather, the discussion of mitigation targets, and liability considerations.

 

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2617.html

 

commentary: http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2640.html …

[knocker]

Research Highlight: Arctic Sea Ice Loss Likely To Be Reversible

 

Scenarios of a sea ice tipping point leading to a permanently ice-free Arctic Ocean were based on oversimplified arguments

 

https://scripps.ucsd.edu/news/research-highlight-arctic-sea-ice-loss-likely-be-reversible

 

Study

 

http://eisenman.ucsd.edu/papers/Wagner-Eisenman-accepted-2015.pdf

[knocker]

Extraordinary heat during the 1930s US Dust Bowl and associated large-scale conditions

 

Abstract

Unusually hot summer conditions occurred during the 1930s over the central United States and undoubtedly contributed to the severity of the Dust Bowl drought. We investigate local and large-scale conditions in association with the extraordinary heat and drought events, making use of novel datasets of observed climate extremes and climate reanalysis covering the past century. We show that the unprecedented summer heat during the Dust Bowl years was likely exacerbated by land-surface feedbacks associated with springtime precipitation deficits. The reanalysis results indicate that these deficits were associated with the coincidence of anomalously warm North Atlantic and Northeast Pacific surface waters and a shift in atmospheric pressure patterns leading to reduced flow of moist air into the central US. Thus, the combination of springtime ocean temperatures and atmospheric flow anomalies, leading to reduced precipitation, also holds potential for enhanced predictability of summer heat events. The results suggest that hot drought, more severe than experienced during the most recent 2011 and 2012 heat waves, is to be expected when ocean temperature anomalies like those observed in the 1930s occur in a world that has seen significant mean warming.

 

http://link.springer.com/article/10.1007/s00382-015-2590-5

 

Synopsis

 

https://www.climatescience.org.au/content/868-warm-oceans-caused-hottest-dust-bowl-years

 

Video explanation of research.

 

[knocker]

Attribution of the record high Central England temperature of 2014 to anthropogenic influences

 

In 2014, Central England experienced its warmest year in a record extending back to 1659. Using both state-of-the-art climate models and empirical techniques, our analysis shows a substantial and significant increase in the likelihood of record-breaking warm years, such as 2014, due to human influences on climate. With 90% confidence we find that anthropogenic forcings on the climate have increased the chances of record warm years in Central England by at least 13-fold. This study points to a large influence of human activities on extreme warm years despite the small region of study and the variable climate of Central England. Our analysis shows that climate change is clearly visible on the local-scale in this case.

 

http://iopscience.iop.org/1748-9326/10/5/054002 (open access)

[knocker]

Dissecting the ocean's unseen waves to learn where the heat, energy and nutrients go

http://www.eurekalert.org/pub_releases/2015-05/pu-dto050715.php

[knocker]

Who'd have thunk it? There *is* an amplification of trends in the tropical troposphere…

 

http://iopscience.iop.org/1748-9326/10/5/054007/article …

[Gray-Wolf]

Who'd have thunk it? There *is* an amplification of trends in the tropical troposphere…

 

http://iopscience.iop.org/1748-9326/10/5/054007/article …

 

And a trend for stronger easterlies in the upper Trop of the deep tropics.

[knocker]

Unabated global mean sea-level rise over the satellite altimeter era

 

The rate of global mean sea-level (GMSL) rise has been suggested to be lower for the past decade compared with the preceding decade as a result of natural variability¹, with an average rate of rise since 1993 of +3.2 ± 0.4 mm yr^−1 (refs 2, 3). However, satellite-based GMSL estimates do not include an allowance for potential instrumental drifts (bias drift^{4, 5}). Here, we report improved bias drift estimates for individual altimeter missions from a refined estimation approach that incorporates new Global Positioning System (GPS) estimates of vertical land movement (VLM). In contrast to previous results (for example, refs 6, 7), we identify significant non-zero systematic drifts that are satellite-specific, most notably affecting the first 6 years of the GMSL record. Applying the bias drift corrections has two implications. First, the GMSL rate (1993 to mid-2014) is systematically reduced to between +2.6 ± 0.4 mm yr^−1 and +2.9 ± 0.4 mm yr^−1, depending on the choice of VLM applied. These rates are in closer agreement with the rate derived from the sum of the observed contributions², GMSL estimated from a comprehensive network of tide gauges with GPS-based VLM applied (updated from ref. 8) and reprocessed ERS-2/Envisat altimetry⁹. Second, in contrast to the previously reported slowing in the rate during the past two decades¹, our corrected GMSL data set indicates an acceleration in sea-level rise (independent of the VLM used), which is of opposite sign to previous estimates and comparable to the accelerated loss of ice from Greenland and to recent projections^{2, 10}, and larger than the twentieth-century acceleration^{2, 8, 10}.

 

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2635.html

 

Arcticle

 

Sea level rise accelerating faster than thought

http://news.sciencemag.org/climate/2015/05/sea-level-rise-accelerating-faster-thought

[knocker]

Audit of the global carbon budget: estimate errors and their impact on uptake uncertainty

 

Abstract. Over the last 5 decades monitoring systems have been developed to detect changes in the accumulation of carbon © in the atmosphere and ocean; however, our ability to detect changes in the behavior of the global C cycle is still hindered by measurement and estimate errors. Here we present a rigorous and flexible framework for assessing the temporal and spatial components of estimate errors and their impact on uncertainty in net C uptake by the biosphere. We present a novel approach for incorporating temporally correlated random error into the error structure of emission estimates. Based on this approach, we conclude that the 2σ uncertainties of the atmospheric growth rate have decreased from 1.2 Pg C yr^−1 in the 1960s to 0.3 Pg C yr^−1 in the 2000s due to an expansion of the atmospheric observation network. The 2σ uncertainties in fossil fuel emissions have increased from 0.3 Pg C yr^−1 in the 1960s to almost 1.0 Pg C yr^−1 during the 2000s due to differences in national reporting errors and differences in energy inventories. Lastly, while land use emissions have remained fairly constant, their errors still remain high and thus their global C uptake uncertainty is not trivial. Currently, the absolute errors in fossil fuel emissions rival the total emissions from land use, highlighting the extent to which fossil fuels dominate the global C budget. Because errors in the atmospheric growth rate have decreased faster than errors in total emissions have increased, a ~20% reduction in the overall uncertainty of net C global uptake has occurred. Given all the major sources of error in the global C budget that we could identify, we are 93% confident that terrestrial C uptake has increased and 97% confident that ocean C uptake has increased over the last 5 decades. Thus, it is clear that arguably one of the most vital ecosystem services currently provided by the biosphere is the continued removal of approximately half of atmospheric CO₂ emissions from the atmosphere, although there are certain environmental costs associated with this service, such as the acidification of ocean waters.

 

http://www.biogeosciences.net/12/2565/2015/bg-12-2565-2015.html

 

Synopsis

 

As carbon emissions climb, so too has the Earth's capacity to remove CO2 from the atmosphere

http://phys.org/news/2015-05-carbon-emissions-climb-earth-capacity.html