mardi 27 février 2018

Climactualités - février 2018

Actualité climatique du mois passé dans laquelle j'entrepose pêle-mêle les articles que j'ai trouvés intéressants (mais j'ai pu, et dû, en louper un certain nombre) ; comme je n'ai pas toute la journée à dédier à la tenue de ce blog je me dispenserai de traduire les articles en français, à chacun donc de se débrouiller avec la langue de Shakespeare en fonction de ses capacités (il y a au demeurant des outils de traduction en ligne assez performants...) ; cependant vous pouvez utiliser l'outil de traduction que Blogger met à votre disposition et que vous trouverez dans le bandeau de droite : 



Sélectionnez d'abord l'anglais si le français n'apparait pas :


Le texte sera alors intégralement traduit en anglais :

Il vous suffira alors de sélectionner le français :


Et tout le texte sera intégralement traduit en français.

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Janvier 2018 : Decadal forecast
metoffice.gov.uk
Forecast issued in January 2018. The forecast will next be updated in January 2019. Further discussion and background information can be found in this research news article.

Figure 3:Observed (black, from Met Office Hadley Centre, GISS and NCDC) and predicted (blue) global average annual surface temperature difference relative to pre-industrial conditions represented by the period 1850-1900. Previous predictions starting from November 1960, 1965, ..., 2010 are shown in red, and 22 model simulations, from the Coupled Model Intercomparison Project phase 5 (CMIP5), that have not been initialised with observations are shown in green. In all cases, the shading represents the probable range, such that the observations are expected to lie within the shading 90% of the time. The most recent forecast (blue) starts from November 2017. All data are rolling 12-month mean values. The gap between the black curves and blue shading arises because the last observed value represents the period November 2016 to October 2017 whereas the first forecast period is November 2017 to October 2018.

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Le 12/02/2018 : Climate-change–driven accelerated sea-level rise detected in the altimeter era

Abstract
Using a 25-y time series of precision satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3, we estimate the climate-change–driven acceleration of global mean sea level over the last 25 y to be 0.084 ± 0.025 mm/y2. Coupled with the average climate-change–driven rate of sea level rise over these same 25 y of 2.9 mm/y, simple extrapolation of the quadratic implies global mean sea level could rise 65 ± 12 cm by 2100 compared with 2005, roughly in agreement with the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) model projections.
Fig. 1.
GMSL from the adjusted processing of ref. 15 (blue) and after removing an estimate for the impacts of the eruption of Mount Pinatubo (12) (red), and after also removing the influence of ENSO (green), fit with a quadratic (black). The acceleration (0.084 mm/y2) is twice the quadratic coefficient.
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Le 2/02/2018 : High-energy, high-fat lifestyle challenges an Arctic apex predator, the polar bear science.sciencemag.org

Abstract
Regional declines in polar bear (Ursus maritimus) populations have been attributed to changing sea ice conditions, but with limited information on the causative mechanisms. By simultaneously measuring field metabolic rates, daily activity patterns, body condition, and foraging success of polar bears moving on the spring sea ice, we found that high metabolic rates (1.6 times greater than previously assumed) coupled with low intake of fat-rich marine mammal prey resulted in an energy deficit for more than half of the bears examined. Activity and movement on the sea ice strongly influenced metabolic demands. Consequently, increases in mobility resulting from ongoing and forecasted declines in and fragmentation of sea ice are likely to increase energy demands and may be an important factor explaining observed declines in body condition and survival.


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Le 13/02/2018 : Increased West Antarctic and unchanged East Antarctic ice discharge over the last 7years
Abstract.
Ice discharge from large ice sheets plays a direct role in determining rates of sea-level rise. We map present day Antarctic-wide surface velocities using Landsat 7 and 8 imagery spanning 2013–2015 and compare to earlier estimates derived from synthetic aperture radar, revealing heterogeneous changes in ice flow since ∼2008.The new mapping provides complete coastal and inland coverage of ice velocity north of 82.4◦S with a mean error of <10myr−1, resulting from multiple overlapping image pairs acquired during the daylight period. Using an optimized flux gate, ice discharge from Antarctica is 1929±40 Gigatons per year (Gtyr−1) in 2015, an increase of 36±15Gtyr−1 from the time of the radar mapping. Flow accelerations across the grounding lines of West Antarctica’s Amundsen Sea Embayment, Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula, account for 88% of this increase. In contrast, glaciers draining the East Antarctic Ice Sheet have been remarkably constant over the period of observation. Including modeled rates of snow accumulation and basal melt, the Antarctic ice sheet lost ice at an average rate of 183±94Gtyr−1 between 2008 and 2015. The modest increase in ice discharge over the past 7 years is contrasted by high rates of ice sheet mass loss and distinct spatial patters of elevation lowering. The West Antarctic Ice Sheet is experiencing high rates of mass loss and displays distinct patterns of elevation lowering that point to a dynamic imbalance. We find modest increase in ice discharge over the past 7 years, which suggests that the recent pattern of mass loss in Antarctica is part of a longer-term phase of enhanced glacier flow initiated in the decades leading up to the first continent-wide radar mapping of ice flow.
Figure 10. Mass budget and change in discharge for the 27 basins defined by Zwally et al. (2002). Mass budget is calculated as described in Table 2 using 2008–2015 average surface mass balance. Change in discharges (circles) calculated by differencing the pan-Antarctic SAR mapping of Rignot et al. (2011a; circa 2008) with weighted average of all 2015 image-pair displacements supplemented with 2009 SAR velocities to fill missing Landsat coverage poleward of 82.5◦S (Scheuchl et al., 2012) with a correction for acquisition time differences to provide an estimate of total discharge for the interior basins (2, 17 and 18; see Table 2). Flux gates FG1 and FG2 are shown with solid green and dashed blue lines, respectively.

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Le 20/02/2018 : Committed sea-level rise under the Paris Agreement and the legacy of delayed mitigation action

Abstract.
Sea-level rise is a major consequence of climate change that will continue long after emissions of greenhouse gases have stopped. The 2015 Paris Agreement aims at reducing climate-related risks by reducing greenhouse gas emissions to net zero and limiting global-mean temperature increase. Here we quantify the effect of these constraints on global sea-level rise until 2300, including Antarctic ice-sheet instabilities. We estimate median sea-level rise between 0.7 and 1.2 m, if net-zero greenhouse gas emissions are sustained until 2300, varying with the pathway of emissions during this century. Temperature stabilization below 2 °C is insufficient to hold median sea-level rise until 2300 below 1.5 m. We find that each 5-year delay in near-term peaking of CO2 emissions increases median year 2300 sea-level rise estimates by ca. 0.2 m, and extreme sea-level rise estimates at the 95th percentile by up to 1 m. Our results underline the importance of near-term mitigation action for limiting long-term sea-level rise risks.
Response of the sea-level contributors to net-zero CO2 scenarios. Time series of the sea-level responses of thermal expansion a, mountain glaciers b, Greenland mass balance c, and Antarctic mass balance d. Sea-level rise is in cm and relative to the year 2000. Colors refer to peak years as in Fig. 1. Shadings show the central 90th percentile range

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Le 21/02/2018 : Europe’s cities face more extreme weather than previously thought

The research, by Newcastle University, UK, has for the first time analysed changes in flooding, droughts and heatwaves for all European cities using all climate models.


Published today in the academic journal Environmental Research Letters, the study shows:
  • a worsening of heatwaves for all 571 cities
  • increasing drought conditions, particularly in southern Europe
  • an increase in river flooding, especially in north-western European cities
  • for the worst projections, increases in all hazards for most European cities 
  • Cork, Derry, Waterford, Wrexham, Carlisle, Glasgow, Chester and Aberdeen could be the worst hit cities in the British Isles for river flooding
  • Even in the lowest case scenario, 85% of UK cities with a river are predicted to face increased river flooding

“Although southern European regions are adapted to cope with droughts, this level of change could be beyond breaking point,” Dr Selma Guerreiro, lead author, explains.


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ENSO
Le 27/02/2018 : climate.gov/enso
La Niña remains in place, but a wave of warm water spreading eastward beneath the surface is a sign of weakening. The dryness across the southern U.S. is consistent with average La Niña conditions.  There is a 55% chance that conditions will return to neutral by the March-May season. The next update will be on March 8.
Visualisation du phénomène ENSO sur le Pacifique Est en décembre 2017.

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GISS L-OTI anomalies de températures vs 1951-1980

27/02/2018 : data.giss.nasa.gov
Note: Gray areas signify missing data.
Note: Ocean data are not used over land nor within 100km of a reporting land station.
Temperature anomalies of January 2018 according to latitude.
Note: Gray areas signify missing data.
Note: Ocean data are not used over land nor within 100km of a reporting land station.
Temperature anomalies of 2017 according to latitude.

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Data Snapshots

27/02/2018 : climate.gov
climate-change-global-temperature
Average surface temperature in 2016 compared to the 1981-2010 average. NOAA Climate.gov map, adapted from Plate 2.1a in State of the Climate in 2016.

History of Global Surface temperature since 1880 source  noaa
Atmospheric carbon dioxide concentrations in parts per million (ppm) for the past 800,000 years, based on EPICA (ice core) data. The peaks and valleys in carbon dioxide levels track the coming and going of ice ages (low carbon dioxide) and warmer interglacials (higher levels). Throughout these cycles, atmospheric carbon dioxide  was never higher than 300 ppm; in 2016, it reached 402.9 ppm (black dot). NOAA Climate.gov, based on EPICA Dome C data (Lüthi, D., et al., 2008) provided by NOAA NCEI Paleoclimatology Program.

This graph ( data source ) shows average area covered by snow in the Northern Hemisphere During March and April as the difference from the 1981-2010 average.

This graph shows monthly gains of the Oceanic Niño Index from 1970 through present.

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Coral Reef Watch
This Figure shows the regions Currently experiencing high levels of heat stress causes coral bleaching That Cdn.
This Figure shows the distribution of the lowest heat stress levels Predicted by at least 60% of the model all members. In other words, there is 60% luck que le displayed heat stress levels will Occur.
NOAA Coral Reef Watch Satellite's Coral Bleaching Alert Area below shows the maximum heat stress During the Third Global Coral Bleaching Event. Experienced Regions That the high heat stress causes coral bleaching That can, from June 1, 2014 to May 31, 2017, are displayed. Alert Level 2 indicates heat stress Widespread coral bleaching and significant mortality. Alert Level 1 indicates significant heat stress coral bleaching. Lower levels of stress May-have Caused Some bleaching as well. More than 70% of coral reefs around the world Experienced the heat stress That can causes bleaching and / or mortality During the three-year long global event.

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Climate Prediction Center
27/02/2018 : cpc.ncep.noaa.gov
Global Tropics Benefits / Hazards 
Last Updated: 02.20.18 Valid: 02.21.18 - 03.06.18
Conditions in the tropics have continued to be influenced by the Madden Julian Oscillation (MJO) during the past week, though the footprint has weakened in comparison to previous weeks. Movement in the MJO signal has stalled since last week, remaining mostly in Phase 7, until progressing into Phase 8 in the past few days. Model guidance is in good agreement that the MJO will move through Phase 8 into Phase 1 during Week-1, possibly weakening further. Forecasts for the MJO signal moving into Week-2 are more uncertain; some models move the signal more quickly through Phase 2 and into Phase 3 during the period. All models do forecast a more significant weakening to the MJO signal in Week-2. La Nina remains active in the central and east Pacific, destructively interfering with the MJO convective envelope as it moves through the Pacific. Forecasts indicate that La Nina is likely to remain active through the winter, most likely transitioning to ENSO-neutral conditions during the spring and early summer.

Moving into the next two weeks, outlooks for tropical cyclone (TC) formation in the western Pacific and Indian Ocean are forecast to be quiet currently. There is a possibility for a TC formation in the Southwest Pacific in Week-1, though confidence remains low at the time, so it is not included on the map. Models also point to possible formation near the Philippines in the western Pacific for Week-2, though uncertainty in the strength of the system leaves confidence low.

Precipitation patterns for Week-1 loosely follow patterns for Phase 8 and Phase 1 MJO impacts; however, with the weakening signal, impacts are not forecast to be significant as the past few weeks. There are high confidence areas of below-average rainfall over the Maritime Continent and eastern Indian Ocean likely due to suppressed convection. The exception is the Coral Sea coast, for which model guidance indicates above-average rainfall. Above-average rainfall is expected for the eastern Pacific, near Hawaii, as well as near the Date Line. These patterns are typical of a Phase 8 MJO, as the convective envelope moves over the central Pacific. The central and eastern equatorial Pacific is forecast to receive below-average rainfall, consistent with impacts expected from the La Nina base state. Above-average precipitation is also forecast for Brazil and parts of the tropical Atlantic. Both model guidance and MJO impacts support this pattern.

Week-2 continues many of the patterns seen in Week-1 as the MJO is forecast to move through Phase 1 into Phase 2 for the latter part of the period. The MJO is also expected to have a dramatic weakening during Week-2, so much of the confidence in the forecast is reduced. Regions of high confidence are supported by dynamical model guidance as well as typical MJO patterns. Below-average rainfall is likely to remain over the Maritime Continent, with possible shifts eastward. Above-average rainfall is still forecast for northeast Australia, as well as the Philippines, for which model guidance shows possible TC formation. Model guidance forecasts above-normal temperatures in southeastern Australia, with anomalies up to 16 degrees C. Below-average rainfall is still forecast for the central Pacific, but the extension into the eastern Pacific has been reduced, due to the interaction with the convective portion of the MJO and the low frequency base state. Above-average rainfall is forecast to continue over Brazil and parts of the Atlantic, as well as the southwestern Indian Ocean. This is likely due to the expected re-emergence of the MJO signal in the Indian Ocean toward the end of Week-2.

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Polar Science Center
27/02/2018psc.apl.uw.edu

The year 2017 finished out with an annually averaged sea ice volume that was the lowest on record with 12,900 km 3 , below 2012 for which the annually averaged volume was 13,500 km3 . This was even though extent and sea ice thickness were at record lows during the early months of 2017 but anomalously little melt for the recent years (Fig 8), brought the ice volume back above record levels.

Average Arctic sea ice volume in January 2018 was 16,000 km3 . This value is 1400 km3 above the previous January record that was set in 2017 with 14,600 km3 and similar to January volumes seen in 2011, 2012 and 2013. January 2018 ice volume was 42% below the maximum in 1979 and 27% below the mean value for 1979-2017. January 2018 ice volume sits right on the long term trend line.

Ice volume was up from the 2017 January minimum despite the fact that January 2018 sea ice extent is tracking near record lows. This is because ice thickness according to PIOMAS is up from 2017 by about 0.12 m.

Ice thickness anomalies for January 2018 relative to 2011-2017 (Fig 6) are positive in the East Siberian Sea and negative in much of the rest of the Arctic. Increased sea ice thickness in the East Siberian Sea is largely due to anomalous sea ice motion (Fig 7.) that likely transported more than normal amounts of sea ice into the East Siberian Sea. A similar pattern of ice thickness anomalies is apparent from CryoSat 2 with thicker sea ice along the Russian side of the Arctic. However, CryoSat 2 (AWI) has sea ice volume at about the same level as 2017.

Figure 8 Comparison of Daily Sea Ice Volume anomalies relative to 1979-2016.
Fig 4.Average Arctic sea ice thickness over the ice-covered regions from PIOMAS for a selection of years. The average thickness is Calculated for the PIOMAS domain by only Including rentals Where ice is thicker than .15 m.
Fig.1  Arctic sea ice volume anomaly from PIOMAS updated once a month. Daily Sea Ice volume anomalies for each day are computed relative to the 1979 to 2017 average for that day of the year. Tickmarks on time axis refer to 1st day of year. The trend for the period 1979- present  is shown in blue. Shaded areas show one and two standard deviations from the trend. Error bars indicate the uncertainty of the  monthly anomaly plotted once per year.
Fig. 2 Total Arctic sea ice volume from PIOMAS showing the volume of the mean annual cycle, and from 2010-2018. Shaded areas indicate one and two standard deviations from the mean.
Fig.3 Monthly Sea Ice Volume from PIOMAS for April and Sep
Fig 6. PIOMAS Ice Thickness Anomaly for January 2018 relative to 2011-2017.




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Arctic Data archive system (ADS)
27/02/2018 : ads.nipr.ac.jp
Arctic sea ice extent.

Antarctic sea ice extent.

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C'est si vrai, en riant avec What on earth? comics !


Le consensus est une légende, ce graphique en est la preuve !


La meilleure façon de lutter contre le réchauffement climatique c'est encore de faire disparaître tout ce qui l'évoque.
Moi d'abord, mes petits-enfants j'en ai rien à faire (traduction libre)

Même les marmottes font l'autruche. 

Nos investissements détruisent peut-être la planète, mais...nous en avons besoin pour sauvegarder votre avenir !







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