New Research

[cheeky_monkey]

14 hours ago, Devonian said:

That's a bit vague. Which climatologist(s)? If it was Tim Ball then LOL!

nope wasnt

[knocker]

Oh look! Another hockey stick:

East Asian warm season temperature variations over the past two millennia

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East Asia has experienced strong warming since the 1960s accompanied by an increased frequency of heat waves and shrinking glaciers over the Tibetan Plateau and the Tien Shan. Here, we place the recent warmth in a long-term perspective by presenting a new spatially resolved warm-season (May-September) temperature reconstruction for the period 1–2000 CE using 59 multiproxy records from a wide range of East Asian regions. Our Bayesian Hierarchical Model (BHM) based reconstructions generally agree with earlier shorter regional temperature reconstructions but are more stable due to additional temperature sensitive proxies. We find a rather warm period during the first two centuries CE, followed by a multi-century long cooling period and again a warm interval covering the 900–1200 CE period (Medieval Climate Anomaly, MCA). The interval from 1450 to 1850 CE (Little Ice Age, LIA) was characterized by cooler conditions and the last 150 years are characterized by a continuous warming until recent times. Our results also suggest that the 1990s were likely the warmest decade in at least 1200 years. The comparison between an ensemble of climate model simulations and our summer reconstructions since 850 CE shows good agreement and an important role of internal variability and external forcing on multi-decadal time-scales.

https://www.nature.com/articles/s41598-018-26038-8

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See Fifteen Years of Change in the Arctic

https://earthobservatory.nasa.gov/blogs/earthmatters/2018/04/23/see-fifteen-years-of-change-in-the-arctic/

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Does global warming make tropical cyclones stronger?

http://www.realclimate.org/index.php/archives/2018/05/does-global-warming-make-tropical-cyclones-stronger/

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Importance of late fall ENSO teleconnection in the Euro-Atlantic sector

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Recent studies have indicated the importance of fall climate forcings and teleconnections in influencing the climate of the northern mid-to-high latitudes. Here, we present some exploratory analyses using observational data and seasonal hindcasts, with the aim of highlighting the potential of the El Niño-Southern Oscillation (ENSO) as a driver of climate variability during boreal late fall/early winter (November/December) in the North Atlantic-European sector and motivating further research on this relatively unexplored topic. The atmospheric ENSO teleconnection in November/December is reminiscent of the East Atlantic pattern and distinct from the well-known arching extratropical Rossby wavetrain found from January to March. Temperature and precipitation over Europe in November are positively correlated with the Niño3.4 index, which suggests a potentially important ENSO climate impact during late fall. In particular, the ENSO-related temperature anomaly extends over a much larger area than during the subsequent winter months. We discuss the implications of these results and pose some research questions.

https://journals.ametsoc.org/doi/10.1175/BAMS-D-17-0020.1

Article

Pacific influences European weather

https://www.sciencedaily.com/releases/2018/03/180321091016.htm

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Heat waves in Finland: present and projected summertime extreme temperatures and their associated circulation patterns

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The number and intensity of individual hot days affecting Finland in the current and future climate is investigated together with the circulation patterns associated with the hot days. In addition, the number, length and intensity of heat waves lasting at least 3 days is also considered. ERA‐Interim reanalysis data and both direct model output and bias‐corrected data for historical and future climate [representative concentration pathway 4.5 (RCP4.5) scenario] simulations from 17 global climate models are analysed. Three intensities of heat waves and hot days are defined based on daily mean temperature thresholds of 20, 24 and 28 °C. The percentage of summertime days which exceed these temperature thresholds is shown to increase in the future. In ERA‐Interim, 24% of summertime days in southern Finland exceed the lowest temperature threshold while none exceed the highest temperature threshold. Under the RCP4.5 scenario these values increase to 47 and 1%, respectively. Larger relative changes occur in northern Finland. Heat waves are also longer in the RCP4.5 simulations than in the historical simulations. In southern Finland, the mean length of a heat wave where the 20 °C daily mean temperature is exceeded is 6.1 days in the historical simulations but increases to 9.4 days in the RCP4.5 simulations. The hot days in both northern and southern Finland are associated with a statistically significant positive pressure anomaly over Finland and to the east to Finland and a statistically significant negative pressure anomaly over Russia between 90 and 120°E. These pressure anomalies were evident for all intensities of hot days in the current climate and the future climate. The magnitude of the pressure anomalies increases as the daily mean temperature threshold increases. However, for hot days which exceed the same daily mean temperature threshold, the pressure anomalies are weaker in the RCP4.5 simulations than in the historical or ERA‐Interim data.

 

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5253

 

Edited July 16, 2018 by knocker

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Understanding, modeling and predicting weather and climate extremes: Challenges and opportunities

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Weather and climate extremes are identified as major areas necessitating further progress in climate research and have thus been selected as one of the World Climate Research Programme (WCRP) Grand Challenges. Here, we provide an overview of current challenges and opportunities for scientific progress and cross-community collaboration on the topic of understanding, modeling and predicting extreme events based on an expert workshop organized as part of the implementation of the WCRP Grand Challenge on Weather and Climate Extremes. In general, the development of an extreme event depends on a favorable initial state, the presence of large-scale drivers, and positive local feedbacks, as well as stochastic processes. We, therefore, elaborate on the scientific challenges related to large-scale drivers and local-to-regional feedback processes leading to extreme events. A better understanding of the drivers and processes will improve the prediction of extremes and will support process-based evaluation of the representation of weather and climate extremes in climate model simulations. Further, we discuss how to address these challenges by focusing on short-duration (less than three days) and long-duration (weeks to months) extreme events, their underlying mechanisms and approaches for their evaluation and prediction.

https://www.sciencedirect.com/science/article/pii/S2212094717300440#bbib44

[knocker]

Does a slow AMOC increase the rate of global warming?

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Established understanding of the AMOC (sometimes popularly called Gulf Stream System) says that a weaker AMOC leads to a slightly cooler global mean surface temperature due to changes in ocean heat storage. But now, a new paper in Nature claims the opposite and even predicts a phase of rapid global warming. What’s the story?

http://www.realclimate.org/index.php/archives/2018/07/does-a-slow-amoc-increase-the-rate-of-glob

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New research show blueprint for El Niño diversity
http://emps.exeter.ac.uk/news-events/news/articles/newresearchshowblueprintf.html

 

https://www.nature.com/articles/s41586-018-0252-6.epdf?author_access_token=WvQbSpQvWAi-aPM29o_YgNRgN0jAjWel9jnR3ZoTv0MvbShUdbnL9czve3oNcK5VOiset1l1GPhGCkmW01rDMTgioW9fAmr4lxyDh2nxUG8MsfGSaVc2UI07DuIynsSVCfegTPLNetmArzt5-194Cw%3D%3D

Edited July 27, 2018 by knocker

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Recent enhanced high-summer North Atlantic Jet variability emerges from three-century context

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A recent increase in mid-latitude extreme weather events has been linked to Northern Hemisphere polar jet stream anomalies. To put recent trends in a historical perspective, long-term records of jet stream variability are needed. Here we combine two tree-ring records from the British Isles and the northeastern Mediterranean to reconstruct variability in the latitudinal position of the high-summer North Atlantic Jet (NAJ) back to 1725 CE. We find that northward NAJ anomalies have resulted in heatwaves and droughts in northwestern Europe and southward anomalies have promoted wildfires in southeastern Europe. We further find an unprecedented increase in NAJ variance since the 1960s, which co-occurs with enhanced late twentieth century variance in the Central and North Pacific Basin. Our results suggest increased late twentieth century interannual meridional jet stream variability and support more sinuous jet stream patterns and quasi-resonant amplification as potential dynamic pathways for Arctic warming to influence mid-latitude weather.

https://www.nature.com/articles/s41467-017-02699-3

[knocker]

Climate change and severe thunderstorms

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The response of severe thunderstorms to a changing climate is a rapidly growing area of research. Severe thunderstorms are one of the largest contributors to global losses in excess of USD $10 billion per year in terms of property and agriculture, as well as dozens of fatalities. Phenomena associated with severe thunderstorms such as large hail (greater than 2 cm), damaging winds (greater than 90 kmh−1), and tornadoes pose a global threat, and have been documented on every continent except Antarctica. Limitations of observational records for assessing past trends have driven a variety of approaches to not only characterize the past occurrence but provide a baseline against which future projections can be interpreted. These proxy methods have included using environments or conditions favorable to the development of thunderstorms and directly simulating storm updrafts using dynamic downscaling. Both methodologies have demonstrated pronounced changes to the frequency of days producing severe thunderstorms. Major impacts of a strongly warmed climate include a general increase in the length of the season in both the fall and spring associated with increased thermal instability and increased frequency of severe days by the late 21st century. While earlier studies noted changes to vertical wind shear decreasing frequency, recent studies have illustrated that this change appears not to coincide with days which are unstable. Questions remain as to whether the likelihood of storm initiation decreases, whether all storms which now produce severe weather will maintain their physical structure in a warmer world, and how these changes to storm frequency and or intensity may manifest for each of the threats posed by tornadoes, hail, and damaging winds. Expansion of the existing understanding globally is identified as an area of needed future research, together with meaningful consideration of both the influence of climate variability and indirect implications of anthropogenic modification of the physical environment.

http://climatescience.oxfordre.com/view/10.1093/acrefore/9780190228620.001.0001/acrefore-9780190228620-e-62

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ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing

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El Niño and Southern Oscillation (ENSO) is the most prominent year‐to‐year climate fluctuation on Earth, alternating between anomalously warm (El Niño) and cold (La Niña) sea surface temperature (SST) conditions in the tropical Pacific. ENSO exerts its impacts on remote regions of the globe through atmospheric teleconnections, affecting extreme weather events worldwide. However, these teleconnections are inherently nonlinear and sensitive to ENSO SST anomaly patterns and amplitudes. In addition, teleconnections are modulated by variability in the oceanic and atmopsheric mean state outside the tropics and by land and sea ice extent. The character of ENSO as well as the ocean mean state have changed since the 1990s, which might be due to either natural variability or anthropogenic forcing, or their combined influences. This has resulted in changes in ENSO atmospheric teleconnections in terms of precipitation and temperature in various parts of the globe. In addition, changes in ENSO teleconnection patterns have affected their predictability and the statistics of extreme events. However, the short observational record does not allow us to clearly distinguish which changes are robust and which are not. Climate models suggest that ENSO teleconnections will change because the mean atmospheric circulation will change due to anthropogenic forcing in the 21st century, which is independent of whether ENSO properties change or not. However, future ENSO teleconnection changes do not currently show strong intermodel agreement from region to region, highlighting the importance of identifying factors that affect uncertainty in future model projections.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017RG000568

[knocker]

 

A new paper on ENSO teleconnections to Europe in early winter

Seasonal Prediction from Arctic Sea Surface Temperatures: Opportunities and Pitfalls

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Abstract

Arctic sea ice extent and sea surface temperature (SST) anomalies have been shown to be skillful predictors of weather anomalies in the midlatitudes on the seasonal time scale. In particular, below-normal sea ice extent in the Barents Sea in fall has sometimes preceded cold winters in parts of Eurasia. Here we explore the potential for predicting seasonal surface air temperature (SAT) anomalies in Europe from seasonal SST anomalies in the Nordic Seas throughout the year. First, we show that fall SST anomalies not just in the Barents Sea, but also in the Norwegian Sea, have the potential to predict wintertime SAT anomalies in Europe. Norwegian Sea SST anomalies in spring are also significant predictors of European SAT anomalies in summer. Second, we demonstrate that the potential for prediction is sensitive to trends in the data. In particular, the lagged correlation between Norwegian Sea SST anomalies in spring and European SAT anomalies in summer is considerably higher for raw data than linearly detrended data, largely due to warming SST and SAT trends in recent decades. Third, we show that the potential for prediction has not been stationary in time. One key result is that, according to two 20th century reanalyses, the strength of the negative lagged correlation between Barents Sea SST anomalies in fall and European SAT anomalies in winter after 1979 is unprecedented since 1900.

https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-18-0016.1#/doi/abs/10.1175/JCLI-D-18-0097.1

Edited August 8, 2018 by knocker

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The influence of Arctic amplification on mid-latitude summer circulation

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Accelerated warming in the Arctic, as compared to the rest of the globe, might have profound impacts on mid-latitude weather. Most studies analyzing Arctic links to mid-latitude weather focused on winter, yet recent summers have seen strong reductions in sea-ice extent and snow cover, a weakened equator-to-pole thermal gradient and associated weakening of the mid-latitude circulation. We review the scientific evidence behind three leading hypotheses on the influence of Arctic changes on mid-latitude summer weather: Weakened storm tracks, shifted jet streams, and amplified quasi-stationary waves. We show that interactions between Arctic teleconnections and other remote and regional feedback processes could lead to more persistent hot-dry extremes in the mid-latitudes. The exact nature of these non-linear interactions is not well quantified but they provide potential high-impact risks for society.

https://www.nature.com/articles/s41467-018-05256-8

[knocker]

Satellite-derived sea ice export and its impact on Arctic ice mass balance

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Abstract. Sea ice volume export through the Fram Strait represents an important freshwater input to the North Atlantic, which could in turn modulate the intensity of the thermohaline circulation. It also contributes significantly to variations in Arctic ice mass balance. We present the first estimates of winter sea ice volume export through the Fram Strait using CryoSat-2 sea ice thickness retrievals and three different ice drift products for the years 2010 to 2017. The monthly export varies between −21 and −540km³. We find that ice drift variability is the main driver of annual and interannual ice volume export variability and that the interannual variations in the ice drift are driven by large-scale variability in the atmospheric circulation captured by the Arctic Oscillation and North Atlantic Oscillation indices. On shorter timescale, however, the seasonal cycle is also driven by the mean thickness of exported sea ice, typically peaking in March. Considering Arctic winter multi-year ice volume changes, 54% of their variability can be explained by the variations in ice volume export through the Fram Strait.

https://www.the-cryosphere.net/12/3017/2018/

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Recent Third Pole’s rapid warming accompanies cryospheric melt and water cycle intensification and interactions between monsoon and environment: multi-disciplinary approach with observation, modeling and analysis (open access)

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Abstract

This mini-review paper presents the latest development in multi-disciplinary Third Pole researches and associated recommendations in the context of current unprecedented warming in the Third Pole’s past 2000 years

The Third Pole (TP) is experiencing rapid warming and is currently in its warmest period in the past 2000 years. This paper reviews the latest development in multi-disciplinary TP research associated with this warming. The rapid warming facilitates intense and broad glacier melt over most of TP, although some glaciers in the northwest are advancing. By heating the atmosphere and reducing snow/ice albedo, aerosols also contribute to the glaciers melting. Glacier melt is accompanied by lake expansion and intensification of the water cycle over the TP. Precipitation has increased over the eastern and northwestern TP. Meanwhile, the TP is greening and most regions are experiencing advancing phenological trends although over the southwest there is a spring phenological delay mainly in response to the recent decline in spring precipitation. Atmospheric and terrestrial thermal and dynamical processes over the TP affect the Asian monsoon at different scales. Recent evidence indicates substantial roles that Meso-scale Convective Systems play in TP’s precipitation as well as an association between soil moisture anomalies in TP and the Indian monsoon. Moreover, an increase in geo-hazard events has been associated with recent environmental changes, some of which have had catastrophic consequences caused by glacial lake outbursts and landslides. Active debris flows are growing in both frequency of occurrences and spatial scale. Meanwhile, new types of disasters, such as the twin ice avalanches in Ali in 2016, are now appearing in the region. Adaptation and mitigation measures should be taken to help societies’ preparation for future environmental challenges. Some key issues for future TP studies are also discussed.

https://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-17-0057.1

[knocker]

Looks like we have put more heat into the ocean than originally thought

Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

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The ocean is the main source of thermal inertia in the climate system1. During recent decades, ocean heat uptake has been quantified by using hydrographic temperature measurements and data from the Argo float program, which expanded its coverage after 20072,3. However, these estimates all use the same imperfect ocean dataset and share additional uncertainties resulting from sparse coverage, especially before 20074,5. Here we provide an independent estimate by using measurements of atmospheric oxygen (O2) and carbon dioxide (CO2)—levels of which increase as the ocean warms and releases gases—as a whole-ocean thermometer. We show that the ocean gained 1.33 ± 0.20  × 1022 joules of heat per year between 1991 and 2016, equivalent to a planetary energy imbalance of 0.83 ± 0.11 watts per square metre of Earth’s surface. We also find that the ocean-warming effect that led to the outgassing of O2 and CO2 can be isolated from the direct effects of anthropogenic emissions and CO2 sinks. Our result—which relies on high-precision O2 measurements dating back to 19916—suggests that ocean warming is at the high end of previous estimates, with implications for policy-relevant measurements of the Earth response to climate change, such as climate sensitivity to greenhouse gases7 and the thermal component of sea-level rise8.

https://www.nature.com/articles/s41586-018-0651-8

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Improved seasonal predictions of Arctic sea ice using satellite sea-ice thickness estimates

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CryoSat-2 satellite sea-ice thickness estimates have been assimilated within the Met Office’s Global Seasonal (GloSea) coupled ensemble prediction system, which leads to a significant improvement in the skill of September Arctic sea-ice predictions made from May.

In a study recently published by the EGU journal The Cryosphere, and led by Dr Ed Blockley, manager of the Polar Climate Group within the Met Office Hadley Centre, the impact of including sea-ice thickness information within the initial conditions of a global, coupled seasonal forecasting system has been investigated for the first time.

Although model-based forecasting systems have been used successfully for seasonal prediction of mid-latitude weather and climate for some time, now their application to Arctic sea-ice prediction is much less mature. Although the use of these dynamical models for seasonal sea-ice prediction is still in its relative infancy, several studies have demonstrated skill in retrospective forecasts of September Arctic sea ice extent made from spring. However, these studies were not able to match the potential skill suggested by so-called “perfect model” studies, where the initial state of the model is known precisely. This implies that there is potential for further improving the skill of these models by performing seasonal forecasts from a more realistic initial state. Furthermore, several studies over the last decade have found that winter sea-ice thickness provides important preconditioning for the evolution of Arctic sea ice through the summer melt season. This suggests that seasonal predictions of Arctic summer sea ice, made by these forecast models, could be improved by specifying a more realistic representation of sea-ice thickness when initialising these models.

“We used the Met Office’s Global Seasonal coupled ensemble prediction system and incorporated satellite sea-ice thickness measurements, derived from the European Space Agency’s CryoSat-2 satellite by the Centre for Polar Observation and Modelling, within the initialisation process” explains Dr Blockley. “We compared forecasts from a large ensemble of GloSea seasonal predictions, performed over the period 2011-2015, against a control experiment that did not include any observations of sea-ice thickness. We show a significant improvement in forecasts of September Arctic sea-ice edge location made from May, with a reduction of Integrated Ice Edge Error of around 37%.”

Human activity in the Arctic is increasing in response to declining sea-ice cover and access to the Arctic Ocean is becoming more important for socio-economic reasons. Human activities in the Arctic include commercial ventures like tourism, mineral and oil extraction, fishing and shipping, as well as traditional activities such as subsistence hunting and fishing, search and rescue, and community re-supply. Accurate forecasts of Arctic sea ice on all timescales are thus becoming increasingly important for the safety of human activities in the Arctic. In particular, improved knowledge of sea ice on seasonal timescales (approx. 90 days) allows for improved planning which should lead to a reduction in risk and operational costs for human activities in the Arctic Ocean.

https://applicate.eu/news/158-improved-seasonal-predictions-of-arctic-sea-ice-using-satellite-sea-ice-thickness-estimates

[knocker]

The key role of background sea surface temperature over the cold tongue in asymmetric responses of the Arctic stratosphere to El Niño–Southern Oscillation

http://iopscience.iop.org/article/10.1088/1748-9326/aae79b/meta

[knocker]

Societal causes of, and responses to, ocean acidification

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Abstract

Major climate and ecological changes affect the world’s oceans leading to a number of responses including increasing water temperatures, changing weather patterns, shrinking ice-sheets, temperature-driven shifts in marine species ranges, biodiversity loss and bleaching of coral reefs. In addition, ocean pH is falling, a process known as ocean acidification (OA). The root cause of OA lies in human policies and behaviours driving society’s dependence on fossil fuels, resulting in elevated CO2 concentrations in the atmosphere. In this review, we detail the state of knowledge of the causes of, and potential responses to, OA with particular focus on Swedish coastal seas. We also discuss present knowledge gaps and implementation needs.

https://rd.springer.com/article/10.1007%2Fs13280-018-1103-2

[knocker]

Quite an interesting tweet thread on the Younger Dryas

 

Edited November 16, 2018 by knocker

[knocker]

Radiosondes Show That After Decades of Cooling, the Lower Stratosphere Is Now Warming

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Abstract

Since the mid‐twentieth century, radiosonde and satellite measurements show that the troposphere has warmed and the stratosphere has cooled. These changes are primarily due to increasing concentrations of well‐mixed greenhouse gases and the depletion of stratospheric ozone. In response to continued greenhouse gas increases and stratospheric ozone depletion, climate models project continued tropospheric warming and stratospheric cooling over the coming decades. Global average satellite observations of lower stratospheric temperatures exhibit no significant trends since the turn of the century. In contrast, an analysis of vertically resolved radiosonde measurements from 60 stations shows an increase of lower stratospheric temperature since the turn of the century at altitudes between 15 and 30 km and over most continents. Trend estimates are somewhat sensitive to homogeneity assessment choices, but all investigated radiosonde data sets suggest a change from late twentieth century cooling to early 21st century warming in the lower stratosphere, which is consistent with a reversal from ozone depletion to recovery from the effects of ozone‐depleting substances. In comparison, satellite observations at the radiosonde locations show only minor early 21st century warming, possibly due to the compensating effects of continued cooling above the radiosonde altitude range.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018JD028901#.W_N0tbiL7tA.twitter

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Edited November 29, 2018 by knocker

[tablet]

On ‎14‎/‎05‎/‎2018 at 08:55, knocker said:

Powerful hurricanes strengthen faster now than 30 years ago

https://www.eurekalert.org/pub_releases/2018-05/dnnl-phs050818.php

where is that happening then Knocker ?

 source - Ryan Moue

source of charts - Klotzbach et al 2018

https://journals.ametsoc.org/doi/10.1175/BAMS-D-17-0184.1

 

 

 

[knocker]

 

Edited November 30, 2018 by knocker