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jethro

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Posted
  • Location: Camborne
  • Location: Camborne

Investigating climate change’s ‘humidity paradox’

Water vapour is fundamental to life on Earth. As well as being a greenhouse gas, water vapour is the basis for clouds and rain. Therefore, it sustains plants, forests and our ability to grow food. 

A lack of water vapour in the air can influence the intensity and frequency of wildfires. An abundance combined with high temperatures can cause heat stress in people and animals. 

It is, therefore, crucial that scientists understand how humidity – how much water vapour there is in the air – is changing, and could change, as global temperatures rise.

In a new dataset and accompanying paper, my co-authors and I explore how different aspects of humidity are changing in contrasting ways over the world’s oceans.

https://www.carbonbrief.org/guest-post-investigating-climate-changes-humidity-paradox?utm_campaign=Carbon Brief Weekly Briefing&utm_content=20201204&utm_medium=email&utm_source=Revue newsletter

 

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Posted
  • Location: Camborne
  • Location: Camborne

Stratospheric drivers of extreme events at the Earth’s surface

The stratosphere, the layer of the atmosphere at heights between 10-50 km, is an important      

source of variability for the weather and climate at the Earth’s surface on timescales of weeks

to decades. Since the stratospheric circulation evolves more slowly than that of the troposphere

below, it can contribute to predictability at the surface. Our synthesis of studies on the

coupling between the stratosphere and the troposphere reveals that the stratosphere also

contributes substantially to a wide range of climate-related extreme events. These extreme

events include cold air outbreaks and extreme heat, air pollution, wildfires, wind extremes,

and storm clusters, as well as changes in tropical cyclones and sea ice cover, and they can

have devastating consequences for human health, infrastructure, and ecosystems. A better

understanding of the vertical coupling in the atmosphere, along with improved representation

in numerical models, is therefore expected to help predict extreme events on timescales from

weeks to decades in terms of the event type, magnitude, frequency, location, and timing.

With a better understanding of stratosphere-troposphere coupling, it may be possible to link

more tropospheric extremes to stratospheric forcing, which will be crucial for emergency

planning and management.

https://www.nature.com/articles/s43247-020-00060-z

Edited by knocker
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Posted
  • Location: Camborne
  • Location: Camborne

Changes in Atlantic Water circulation patterns and volume transports North of Svalbard over the last 12 years (2008‐2020)

Abstract

Atlantic Water (AW) enters the Arctic through Fram Strait as the West Spitsbergen Current (WSC). When reaching the south of Yermak Plateau, the WSC splits into the Svalbard, Yermak Pass and Yermak Branches. Downstream of Yermak Plateau, AW pathways remain unclear and uncertainties persist on how AW branches eventually merge and contribute to the boundary current along the continental slope. We took advantage of the good performance of the 1/12° Mercator Ocean model in the Western Nansen Basin (WNB) to examine the AW circulation and volume transports in the area. The model showed that the circulation changed in 2008‐2020. The Yermak Branch strengthened over the northern Yermak Plateau, feeding the Return Yermak Branch along the eastern flank of the Plateau. Coincidently, AW recirculations towards Fram Strait shifted further north. Downstream of the Yermak Plateau, an offshore current developed above the 3800 m isobath, fed by waters from the Yermak Plateau tip. East of 18°E, enhanced mesoscale activity from the boundary current injected additional AW basin‐ward, further contributing to the offshore circulation. A recurrent anticyclonic circulation in Sofia Deep developed, which also occasionally fed the western part of the offshore flow. West of Yermak Plateau, the Transpolar Drift likely shifted westward while AW recirculations progressed further north. The intensification of the circulation coincided with an overall warming in the upper WNB (0‐1000 m), consistent with the progression of AW. This regional description of the changing circulation provides a background for the interpretation of upcoming observations.

Plain language summary

Atlantic Water (AW) is the main source of heat and salt to the Arctic Ocean. We used 12 years of a high‐resolution model to examine the recent evolution of the circulation, volume transport and properties of AW in their major entry region, the Western Nansen Basin (WNB). The model showed the development of new pathways of AW, the intensification of the circulation north of Svalbard, along with the progressive warming and thickening of the Atlantic Water layer. These changes are important for the distribution of heat and salt to the Eurasian basin interior and for the sea‐ice cover evolution.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JC016825

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Posted
  • Location: Camborne
  • Location: Camborne

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

Abstract

Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in particular in the North Atlantic–European (NAE) region. While the stratospheric forcing often projects onto the North Atlantic Oscillation (NAO), the tropospheric response to SSW events, if any, is highly variable, and what determines the existence, location, timing, and strength of the downward impact remains an open question. We here explore how the variable tropospheric response to SSW events in the NAE region can be characterized in terms of a refined set of seven weather regimes and if the tropospheric flow in the North Atlantic region around the onset of SSW events is an indicator of the subsequent downward impact. The weather regime analysis reveals the Greenland blocking (GL) and Atlantic trough (AT) regimes as the most frequent large-scale patterns in the weeks following an SSW. While the GL regime is dominated by high pressure over Greenland, AT is dominated by a southeastward-shifted storm track in the North Atlantic. The flow evolution associated with GL and the associated cold conditions over Europe in the weeks following an SSW occur most frequently if a blocking situation over western Europe and the North Sea (European blocking) prevailed around the SSW onset. In contrast, an AT regime associated with mild conditions over Europe is more likely following the SSW event if GL occurs already around SSW onset. For the remaining tropospheric flow regimes during SSW onset we cannot identify a dominant flow evolution. Although it remains unclear what causes these relationships, the results suggest that specific tropospheric states in the days around the onset of the SSW are an indicator of the subsequent tropospheric flow evolution in the aftermath of an SSW, which could provide crucial guidance for subseasonal prediction.

https://wcd.copernicus.org/articles/1/373/2020/

 

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Posted
  • Location: Camborne
  • Location: Camborne

Recent global decline of CO2 fertilization effects on vegetation photosynthesis

A decline in the carbon fertilization effect

One source of uncertainty in climate science is how the carbon fertilization effect (CFE) will contribute to mitigation of anthropogenic climate change. Wang et al. explored the temporal dynamics of CFE on vegetation photosynthesis at the global scale. There has been a decline over recent decades in the contribution of CFE to vegetation photosynthesis, perhaps owing to the limiting effects of plant nutrients such as nitrogen and phosphorus. This declining trend has not been adequately accounted for in carbon cycle models. CFE thus has limitations for long-term mitigation of climate change, and future warming might currently be underestimated.

Science, this issue p. 1295

Abstract

The enhanced vegetation productivity driven by increased concentrations of carbon dioxide (CO2) [i.e., the CO2 fertilization effect (CFE)] sustains an important negative feedback on climate warming, but the temporal dynamics of CFE remain unclear. Using multiple long-term satellite- and ground-based datasets, we showed that global CFE has declined across most terrestrial regions of the globe from 1982 to 2015, correlating well with changing nutrient concentrations and availability of soil water. Current carbon cycle models also demonstrate a declining CFE trend, albeit one substantially weaker than that from the global observations. This declining trend in the forcing of terrestrial carbon sinks by increasing amounts of atmospheric CO2 implies a weakening negative feedback on the climatic system and increased societal dependence on future strategies to mitigate climate warming.

https://science.sciencemag.org/content/370/6522/1295.full

 

 

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Posted
  • Location: Ireland, probably South Tipperary
  • Weather Preferences: Cold, Snow, Windstorms and Thunderstorms
  • Location: Ireland, probably South Tipperary
tc-15-233-2021-avatar-web.png
TC.COPERNICUS.ORG

<p><strong class="journal-contentHeaderColor">Abstract.</strong> We combine satellite observations and numerical models to show that Earth lost 28 trillion tonnes of ice between 1994 and...

Abstract
We combine satellite observations and numerical models to show that Earth lost 28 trillion tonnes of ice between 1994 and 2017. Arctic sea ice (7.6 trillion tonnes), Antarctic ice shelves (6.5 trillion tonnes), mountain glaciers (6.1 trillion tonnes), the Greenland ice sheet (3.8 trillion tonnes), the Antarctic ice sheet (2.5 trillion tonnes), and Southern Ocean sea ice (0.9 trillion tonnes) have all decreased in mass. Just over half (58 %) of the ice loss was from the Northern Hemisphere, and the remainder (42 %) was from the Southern Hemisphere. The rate of ice loss has risen by 57 % since the 1990s – from 0.8 to 1.2 trillion tonnes per year – owing to increased losses from mountain glaciers, Antarctica, Greenland and from Antarctic ice shelves. During the same period, the loss of grounded ice from the Antarctic and Greenland ice sheets and mountain glaciers raised the global sea level by 34.6 ± 3.1 mm. The majority of all ice losses were driven by atmospheric melting (68 % from Arctic sea ice, mountain glaciers ice shelf calving and ice sheet surface mass balance), with the remaining losses (32 % from ice sheet discharge and ice shelf thinning) being driven by oceanic melting. Altogether, these elements of the cryosphere have taken up 3.2 % of the global energy imbalance.

Media article on the paper

5100.jpg?width=1200&height=630&quality=8
WWW.THEGUARDIAN.COM

Rate of loss now in line with worst-case scenarios of the Intergovernmental Panel on Climate Change

And an animation showing where the ice loss comes from and variations over time.

 

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Posted
  • Location: Camborne
  • Location: Camborne

Earth’s Future is a transdisciplinary, Gold Open Access journal examining the state of the planet and its inhabitants, sustainable and resilient societies, the science of the Anthropocene, and predictions of our common future through research articles, reviews and commentaries. 

·                 This Earth's Future special collection covers a broad range of analyses that leverage simulations from the Coupled Model Intercomparison Project 6 (CMIP6). The most impactful consequences of a changing Earth system are often the result of combined effects of multiple physical processes. Therefore, quantifying changes in the Earth's climate system requires characterization of individual phenomena as well as the interactions and uncertainties across the Earth system.

https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)2328-4277.CMIP6TIEI

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Posted
  • Location: Camborne
  • Location: Camborne

Gived current events perhaps worth another look


To the Editor — The idea that rapid Arctic warming might be changing weather patterns at lower latitudes rose to prominence in 2012. At that time, amidst rising global temperatures and record low Arctic sea-ice cover, parts of the mid-latitudes had just experienced a run of extremely cold winters1. Some scientists speculated that these cold snaps were driven by Arctic-induced changes in the atmospheric circulation, pointing to an unexpected 25-year winter cooling trend over Eurasia, an ostensible shift in the Arctic Oscillation and increased meandering of the jet stream as evidence2,3. These tendencies would continue as the Arctic warmed further, they predicted. Such ideas were controversial from the outset. Very quickly, other scientists questioned the idea, arguing that the cooling and circulation trends were not robust and unlikely to continue in the longer term4,5. Jennifer Francis, whose seminal work proposed that Arctic warming was leading to a wavier jet stream, predicted in 2014 that “within a few years, as Arctic amplification continues, we will have enough data to know whether or not we’re right”6.

So, six years on, what has changed? Arctic amplification and sea-ice loss have indeed continued (Fig. 1). But predictions of a more negative Arctic Oscillation, wavier jet stream, colder winters in mid-latitudes or, more specifically, in Eurasia, and more frequent and/or widespread cold extremes have not become reality (Fig. 1). The short-term tendencies from the late 1980s through to early 2010s that fuelled the initial speculation of Arctic influence have not continued over the past decade (Fig. 1). Long-term trends in the Arctic Oscillation and waviness, updated to winter 2019/20, are small and indistinguishable from internal variability (Fig. 1). Temperature-related metrics all indicate warming in the longer term, with fewer and milder cold extremes (Fig. 1). The multidecadal warming of minimum daily temperature is larger than that of average winter temperature (Fig. 1), implying a detectable reduction in mid-latitudes of subseasonal temperature variability7

https://www.nature.com/articles/s41558-020-00954-y

Edited by knocker
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Posted
  • Location: Exeter, Devon, UK. alt 10m asl
  • Location: Exeter, Devon, UK. alt 10m asl

Just seen this in the Guradian - report on a nature geosciences communication paper from today.

4252.jpg?width=1200&height=630&quality=8
WWW.THEGUARDIAN.COM

Decline in system underpinning Gulf Stream could lead to more extreme weather in Europe and higher sea levels on US east coast

 

Link to communication

41561_2021_699_Fig1_HTML.png
WWW.NATURE.COM

The Atlantic Meridional Overturning Circulation (AMOC) is currently distinctly weaker than it has been for the last millennium, according to a synthesis of proxy records derived from a range of techniques.

 

 

 

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Posted
  • Location: Camborne
  • Location: Camborne

Acceleration of western Arctic sea ice loss linked to the Pacific North American pattern

Abstract

Recent rapid Arctic sea-ice reduction has been well documented in observations, reconstructions and model simulations. However, the rate of sea ice loss is highly variable in both time and space. The western Arctic has seen the fastest sea-ice decline, with substantial interannual and decadal variability, but the underlying mechanism remains unclear. Here we demonstrate, through both observations and model simulations, that the Pacific North American (PNA) pattern is an important driver of western Arctic sea-ice variability, accounting for more than 25% of the interannual variance. Our results suggest that the recent persistent positive PNA pattern has led to increased heat and moisture fluxes from local processes and from advection of North Pacific airmasses into the western Arctic. These changes have increased lower-tropospheric temperature, humidity and downwelling longwave radiation in the western Arctic, accelerating sea-ice decline. Our results indicate that the PNA pattern is important for projections of Arctic climate changes, and that greenhouse warming and the resultant persistent positive PNA trend is likely to increase Arctic sea-ice loss

https://www.nature.com/articles/s41467-021-21830-z#Abs1

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Posted
  • Location: Camborne
  • Location: Camborne

Observed Statistical Connections Overestimate the Causal Effects of Arctic Sea Ice Changes on Midlatitude Winter Climate

Abstract

Disentangling the contribution of changing Arctic sea ice to midlatitude winter climate variability remains challenging because of the large internal climate variability in midlatitudes, difficulties separating cause from effect, methodological differences, and uncertainty around whether models adequately simulate connections between Arctic sea ice and midlatitude climate. We use regression analysis to quantify the links between Arctic sea ice and midlatitude winter climate in observations and large initial-condition ensembles of multiple climate models, in both coupled configurations and so-called Atmospheric Model Intercomparison Project (AMIP) configurations, where observed sea ice and/or sea surface temperatures are prescribed. The coupled models capture the observed links in interannual variability between winter Barents–Kara sea ice and Eurasian surface temperature, and between winter Chukchi–Bering sea ice and North American surface temperature. The coupled models also capture the delayed connection between reduced November–December Barents–Kara sea ice, a weakened winter stratospheric polar vortex, and a shift toward the negative phase of the North Atlantic Oscillation in late winter, although this downward impact is weaker than observed. The strength and sign of the connections both vary considerably between individual 35-yr-long ensemble members, highlighting the need for large ensembles to separate robust connections from internal variability. All the aforementioned links are either absent or are substantially weaker in the AMIP experiments prescribed with only observed sea ice variability. We conclude that the causal effects of sea ice variability on midlatitude winter climate are much weaker than suggested by statistical associations, evident in observations and coupled models, because the statistics are inflated by the effects of atmospheric circulation variability on sea ice.

https://journals.ametsoc.org/view/journals/clim/34/8/JCLI-D-20-0293.1.xml

 

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Posted
  • Location: Camborne
  • Location: Camborne

Arctic sea-ice loss fuels extreme European snowfall

Abstract

The loss of Arctic sea-ice has been implicated with severe cold and snowy mid-latitude winters. However, the mechanisms and a direct link remain elusive due to limited observational evidence. Here we present atmospheric water vapour isotope measurements from Arctic Finland during ‘the Beast from the East’—a severe anticyclonic outbreak that brought heavy snowfall and freezing across Europe in February 2018. We find that an anomalously warm Barents Sea, with a 60% ice-free surface, supplied up to 9.3 mm d−1 moisture flux to this cold northeasterly airflow. We demonstrate that approximately 140 gigatonnes of water was evaporated from the Barents Sea during the event, potentially supplying up to 88% of the corresponding fresh snow over northern Europe. Reanalysis data show that from 1979 to 2020, net March evaporation across the Barents Sea increased by approximately 70 kg per square metre of sea-ice lost (r2 = 0.73, P < 0.01), concurrent with a 1.6 mm (water equivalent) per year increase in Europe’s maximum snowfall. Our analysis directly links Arctic sea-ice loss with increased evaporation and extreme snowfall, and signifies that by 2080, an Atlantified ice-free Barents Sea will be a major source of winter moisture for continental Europe.

https://www.nature.com/articles/s41561-021-00719-y

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Posted
  • Location: Camborne
  • Location: Camborne

How ‘high-resolution’ climate models will help Europe plan for extreme weather

Weather, including extreme rainfall, hail, lightning and severe wind gusts. Along with lighting up the skies, these storms frequently cause catastrophic damage. In Europe, for example, the costs run to billions of euros every year.

Scientists expect that the frequency and intensity of convective storms will change as the climate warms. And understanding these changes is crucial to ensuring the resilience of critical infrastructure to extreme weather.

However, accurate projections of convective weather require “high-resolution” climate models. Yet climate services often lack such detailed data and are typically built on the coarse climate model output available.

As a result, adaptation planning – regarding, for example, urban flood management, hail damage to solar panels and crops, and lightning impact on electricity networks – are often left to crude assumptions.

Fortunately, a new generation of climate models – known as “convection-permitting models” (CPMs) – are providing a step change in our ability to project changes in high-impact weather extremes. 

In a pair of new papers, published in Climate Dynamics, we show how recent advances in the use of CPMs are bringing about a step change in the information available for climate change risk assessment in Europe.


https://www.carbonbrief.org/guest-post-how-high-resolution-climate-models-will-help-europe-plan-for-extreme-weather?utm_campaign=Carbon Brief Weekly Briefing&utm_content=20210416&utm_medium=email&utm_source=Revue newsletter

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Posted
  • Location: Ireland - East Coast
  • Location: Ireland - East Coast
On 29/03/2021 at 19:17, Snipper said:
AgEXQVZmSktrazBzVDF5WDVQaG0zYUxjNUEAMA
APPLE.NEWS

Spreading coffee pulp on degraded farmland can turbocharge forest regrowth, researchers discover

Be nice if it worked. 

I don't want to be glib. But working in an American multi National and all that goes with, for instance virtue signalling etc. They open and close coffee shops in the offices and make great noises and announcements about people taking a cup of coffee grounds home with them and every thing is great with the world. For that reason this turns me off as it is indeed right up the hipster self congratulatory world view. 

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Posted
  • Location: Camborne
  • Location: Camborne

Overshooting tipping point thresholds in a changing climate

Abstract

Palaeorecords suggest that the climate system has tipping points, where small changes in forcing cause substantial and irreversible alteration to Earth system components called tipping elements. As atmospheric greenhouse gas concentrations continue to rise as a result of fossil fuel burning, human activity could also trigger tipping, and the impacts would be difficult to adapt to. Previous studies report low global warming thresholds above pre-industrial conditions for key tipping elements such as ice-sheet melt. If so, high contemporary rates of warming imply that exceeding these thresholds is almost inevitable, which is widely assumed to mean that we are now committed to suffering these tipping events. Here we show that this assumption may be flawed, especially for slow-onset tipping elements (such as the collapse of the Atlantic Meridional Overturning Circulation) in our rapidly changing climate. Recently developed theory indicates that a threshold may be temporarily exceeded without prompting a change of system state, if the overshoot time is short compared to the effective timescale of the tipping element. To demonstrate this, we consider transparently simple models of tipping elements with prescribed thresholds, driven by global warming trajectories that peak before returning to stabilize at a global warming level of 1.5 degrees Celsius above the pre-industrial level. These results highlight the importance of accounting for timescales when assessing risks associated with overshooting tipping point thresholds.

https://www.nature.com/articles/s41586-021-03263-2#Sec9

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Posted
  • Location: Camborne
  • Location: Camborne

CMIP5 Intermodel Relationships in the Baseline Southern Ocean Climate System and With Future Projections

Abstract

Climate models exhibit a broad range in the simulated properties of the climate system. In the early historical period, the absolute global mean surface air temperature in Coupled Model Intercomparison Project, Phase 5 (CMIP5) models spans a range of ∼12°C – 15°C. Other climate variables may be linked to global mean temperature, and so accurate representation of the baseline climate state is crucial for meaningful future climate projections. In CMIP5 baseline climate states, statistically significant intermodel correlations between Southern Ocean surface temperature, outgoing shortwave radiation, cloudiness, the position of the mid-latitude eddy-driven jet, and Antarctic sea ice area are found. The baseline temperature relationships extend to projected future changes in the same set of variables, impacting on the projected global mean surface temperature change. Models with initially cooler Southern Ocean tend to exhibit more global warming, and vice versa for initially warmer models. These relationships arise due to a “capacity for change”. For example, cold-biased models tend to have more cloud cover, sea ice, and equatorward jet initially, and thus a greater capacity to lose cloud cover and sea ice, and for the jet to shift poleward under global warming. A first look at emerging data from CMIP6 reveals a shift of the relationship from the Southern Ocean towards the Antarctic region, possibly due to reductions in Southern Ocean biases, such as in westerly wind representation.

Plain Language Summary

Modern simulations of the Earth's climate system differ in some of their large-scale features. For example, in models reported on by the Intergovernmental Panel on Climate Change in the Fifth Assessment Report, the global average temperature ranges between 12°C and 15°C. Global mean temperature is known to be linked to other features, such as wind, clouds, and rainfall. Accurately modeling the present-day climate is important, so that we can have more confidence in the possible futures they simulate under different levels of anthropogenic greenhouse gas emissions. In this study, strong relationships are found between simulated Southern Ocean temperature and the amount of sea ice and clouds. In addition, it is found that the initial Southern Ocean temperature is also related to changes in sea ice and cloud simulated in the future. A model that is cooler initially, for example, tends to have more sea ice and cloud, but also loses more sea ice and cloud in the future, and simulates more global warming.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020EF001873

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Posted
  • Location: Camborne
  • Location: Camborne

Climate change has driven 16% drop in ‘snow meltwater’ from Asia’s high mountains

Climate change is reducing the supply of water from melting snow to many of the largest rivers in Asia, threatening the water security of millions of people, a new study finds.

Asia is home to the world’s “third pole” – the largest volume of fresh water outside of the polar ice sheets. Melting snowpacks and glaciers from this region feed some of the largest rivers in Asia, which more than a billion people rely on for water. However, as climate change causes melting in the region to accelerate, snow and ice reserves in the area are depleting, leading to worries over water insecurity.

The new study finds that, between 1979-99 and 1999-2019, “snow meltwater supply” to rivers in high-mountain Asia dropped by an average of 16%. It adds that, even if warming is limited to 1.5C, there will be further losses of around 6% by the end of the century. Meanwhile, an extremely high future warming scenario would drive a 40% drop in meltwater supply.

The authors of the paper, which is published in Nature Climate Change, add that although melting glaciers often receive “considerable attention” for their contribution to streamflow, the impact of melting snow is often larger than that of glaciers.

https://www.carbonbrief.org/climate-change-has-driven-16-drop-in-snow-meltwater-from-asias-high-mountains

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Posted
  • Location: Camborne
  • Location: Camborne

Amplified Waveguide Teleconnections Along the Polar Front Jet Favor Summer Temperature Extremes Over Northern Eurasia

Abstract

An apparent increase in the frequency of summer temperature extremes over northern Eurasia has been observed in the past decade. Some of these high-impact events were associated with amplified waveguide teleconnections embedded in the polar front jet, but it remains unclear if extreme temperatures are robustly and routinely related to amplified waves along the polar front jet. This study systematically examines relationships between planetary wave activity and temperature extremes using observations, reanalysis, and large-ensemble simulations from multiple climate models. Months with extreme temperatures over northern Eurasia generally have amplified wave activity along the polar front jet, whereas months with near-average temperatures tend to have attenuated wave activity. Waveguide teleconnections are particularly amplified during extremely hot and cold summer months over eastern Europe and western Russia. These findings demonstrate the important role of waveguide teleconnections along the polar front jet in generating regional temperature extremes over northern Eurasia.

Plain Language Summary

Atmospheric circulation anomalies move horizontally across Earth. At a particular location, this can be seen in the passage of low- and high-pressure systems over time, much like the peaks and troughs of an ocean wave. Sometimes these atmospheric waves can become trapped, preventing their northward or southward migration, and are guided predominantly west to east along a common path, and when they do this, they often grow in amplitude. Amplified atmospheric waves may be a cause of prolonged heatwaves, such as those that occurred in eastern Europe and western Russia in summer 2010 and that resulted in 55,000 deaths and economic losses of more than $15 billion. This study examines the relationship between wave activity and summer temperature extremes over northern Eurasia. We find that wave activity tended to be greater than normal during those summer months that had extreme temperatures. In contrast, wave activity was commonly less during months with near-average temperatures. In particular, waves were especially amplified during extremely hot and cold summer months over eastern Europe and western Russia. This work helps to understand the causes of extreme heat waves over northern Eurasia in order that society may be better prepared when they occur.

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093735

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Posted
  • Location: Camborne
  • Location: Camborne

Rapid attribution analysis of the extraordinary heatwave on the Pacific Coast of the US and Canada June 2021

Main findings
● Based on observations and modeling, the occurrence of a heatwave with
maximum daily temperatures (TXx) as observed in the area 45–52 ºN, 119–123
ºW, was virtually impossible without human-caused climate change.
● The observed temperatures were so extreme that they lie far outside the range of
historically observed temperatures. This makes it hard to quantify with
confidence how rare the event was. In the most realistic statistical analysis the
event is estimated to be about a 1 in 1000 year event in today’s climate.
● There are two possible sources of this extreme jump in peak temperatures. The
first is that this is a very low probability event, even in the current climate which
already includes about 1.2°C of global warming -- the statistical equivalent of
really bad luck, albeit aggravated by climate change. The second option is that
nonlinear interactions in the climate have substantially increased the probability
of such extreme heat, much beyond the gradual increase in heat extremes that
has been observed up to now. We need to investigate the second possibility
further, although we note the climate models do not show it. All numbers below
assume that the heatwave was a very low probability event that was not caused
by new nonlinearities.
● With this assumption and combining the results from the analysis of climate
models and weather observations, an event, defined as daily maximum
temperatures (TXx) in the heatwave region, as rare as 1 in a 1000 years would
have been at least 150 times rarer without human-induced climate change.
● Also, this heatwave was about 2°C hotter than it would have been if it had
occurred at the beginning of the industrial revolution (when global mean
temperatures were 1.2°C cooler than today).
● Looking into the future, in a world with 2°C of global warming (0.8°C warmer than
today which at current emission levels would be reached as early as the 2040s ),
this event would have been another degree hotter. An event like this -- currently
estimated to occur only once every 1000 years, would occur roughly every 5 to
10 years in that future world with 2°C of global warming.
In

Link to the report:

https://worldweatherattribution.org/wp-content/uploads/NW-US-extreme-heat-2021-scientific-report-WWA.pdf

Edited by knocker
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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

I take it the German (and others) flooding will see the same 'rapid attribution' of the events there?

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Posted
  • Location: Camborne
  • Location: Camborne

Recent increase in major Atlantic hurricanes may be ‘rebound’ after 1960-1980s lull

To date, there have been five named storms that have formed in the North Atlantic since the “hurricane season” officially began on 1 June.

There has been much discussion over the years about whether the number of these storms each year has been increasing. (There is a separate debate about their increasing intensity.) However, it has been hard to definitively answer this question due to the lack of data from the period before scientists became reliant on satellite records in the late 1970s.

A new paper published this week in Nature Communications attempted to resolve this issue by extending the available data back to the middle of the 1800s.

As Robert McSweeney’s summary of the paper for Carbon Brief explained:

“The updated record suggests that increases in the number of Atlantic hurricanes since the 1980s are “not part of a century-scale increase”, but a rebound from a lull caused by natural variability and human-caused air pollution in the second half of the 20th century.”

However, other scientists he spoke to stressed that these findings are limited to the North Atlantic and do not “necessarily mean the anthropogenic effect on tropical cyclones is marginal”.

https://www.carbonbrief.org/recent-increase-in-major-atlantic-hurricanes-may-be-rebound-after-1960-1980s-lull?utm_campaign=Carbon Brief Weekly Briefing&utm_content=20210716&utm_medium=email&utm_source=Revue Weekly

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  • Location: Camborne
  • Location: Camborne

Drivers of uncertainty in future projections of Madden–Julian Oscillation teleconnections

Abstract

Teleconnections from the Madden–Julian Oscillation (MJO) are a key source of predictability of weather on the extended timescale of about 10–40 d. The MJO teleconnection is sensitive to a number of factors, including the mean dry static stability, the mean flow, and the propagation and intensity characteristics of the MJO, which are traditionally difficult to separate across models. Each of these factors may evolve in response to increasing greenhouse gas emissions, which will impact MJO teleconnections and potentially impact predictability on extended timescales. Current state-of-the-art climate models do not agree on how MJO teleconnections over central and eastern North America will change in a future climate. Here, we use results from the Coupled Model Intercomparison Project Phase 6 (CMIP6) historical and SSP585 experiments in concert with a linear baroclinic model (LBM) to separate and investigate alternate mechanisms explaining why and how boreal winter (January) MJO teleconnections over the North Pacific and North America may change in a future climate and to identify key sources of inter-model uncertainty. LBM simulations suggest that a weakening teleconnection due to increases in tropical dry static stability alone is robust across CMIP6 models and that uncertainty in mean state winds is a key driver of uncertainty in future MJO teleconnections. Uncertainty in future changes to the MJO's intensity, eastward propagation speed, zonal wavenumber, and eastward propagation extent are other important sources of uncertainty in future MJO teleconnections. We find no systematic relationship between future changes in the Rossby wave source and the MJO teleconnection or between changes to the zonal wind or stationary Rossby wave number and the MJO teleconnection over the North Pacific and North America. LBM simulations suggest a reduction of the boreal winter MJO teleconnection over the North Pacific and an uncertain change over North America, with large spread over both regions that lends to weak confidence in the overall outlook. While quantitatively determining the relative importance of MJO versus mean state uncertainties in determining future teleconnections remains a challenge, the LBM simulations suggest that uncertainty in the mean state winds is a larger contributor to the uncertainty in future projections of the MJO teleconnection than the MJO.

https://wcd.copernicus.org/articles/2/653/2021/

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Posted
  • Location: Camborne
  • Location: Camborne

Preliminary analysis concludes Pacific Northwest heat wave was a 1,000-year event…hopefully

An international team of weather and climate experts known as the “World Weather Attribution” project has analyzed the late June heatwave in the U.S. Pacific Northwest and come to a preliminary conclusion that the event was a roughly 1-in-1,000-year event in today’s climate. (The results are preliminary because, while the methods the experts used have been applied to many other published studies like this, this specific analysis has not yet been formally reviewed by other experts.) If they are correct, it would have been at least 150 times rarer before global warming. Theoretically, a 1-in-150,000-year event—so rare, they concluded, that it’s fair to say it would have been “virtually impossible” in pre-industrial times. Taken at face value, it would also mean that events like that aren’t about to become common any time soon.

https://climate.gov/news-features/event-tracker/preliminary-analysis-concludes-pacific-northwest-heat-wave-was-1000-year

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