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jethro

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2 minutes ago, knocker said:

My first thought was that this is at variance with Dr, Francis, et al but of course they discussed that

 

Her initial work focussed on the impacts to the atmosphere over Barrentsz/Kara as they saw 'low ice levels' earlier than other areas of the basin so had the excess acquired 'summer heating' to release before refreeze?

Now we have seen a number of years with the Pacific side of the basin also seeing low summer ice and so extra 'heating' leading to those area to 'shedding' that heat before refreeze could take place (as atmospheric soundings showed us?)

Like adding an extra lead weight to an out of balance wheel will this have 'smoothed out' the flow of the PNJ as it established and so allow it to remain roughly stable all winter?

The other thing is the speed (currently) of the PNJ.

Will such have implications for some of the SSW's we see with the flow powering through any 'deflected' winds trying to impact its flow?

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It would also appear we should have been 0.2c warmer were it not for the 'Greening' of the Planet since 1980?

greening_tamo_2000-2018_th.png
EARTHOBSERVATORY.NASA.GOV

Scientists say the world would be even warmer if not for a surge in plant growth.

 

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The role of Northeast Pacific meltwater events in deglacial climate change

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Abstract

Columbia River megafloods occurred repeatedly during the last deglaciation, but the impacts of this fresh water on Pacific hydrography are largely unknown. To reconstruct changes in ocean circulation during this period, we used a numerical model to simulate the flow trajectory of Columbia River megafloods and compiled records of sea surface temperature, paleo-salinity, and deep-water radiocarbon from marine sediment cores in the Northeast Pacific. The North Pacific sea surface cooled and freshened during the early deglacial (19.0-16.5 ka) and Younger Dryas (12.9-11.7 ka) intervals, coincident with the appearance of subsurface water masses depleted in radiocarbon relative to the sea surface. We infer that Pacific meltwater fluxes contributed to net Northern Hemisphere cooling prior to North Atlantic Heinrich Events, and again during the Younger Dryas stadial. Abrupt warming in the Northeast Pacific similarly contributed to hemispheric warming during the Bølling and Holocene transitions. These findings underscore the importance of changes in North Pacific freshwater fluxes and circulation in deglacial climate events.

https://advances.sciencemag.org/content/6/9/eaay2915

News release

https://www.eurekalert.org/pub_releases/2020-02/osu-ffi022620.php

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Indian Ocean phenomenon spells climate trouble for Australia

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New international research has found a worrying change in the Indian Ocean's surface temperatures that puts southeast Australia on course for increasingly hot and dry conditions.

The work led by The Australian National University (ANU) and the ARC Centre of Excellence for Climate Extremes has a silver lining, helping to improve our understanding of climate variations and the management of risk caused by Indian Ocean variability.

Lead researcher Professor Nerilie Abram said the phenomenon her team studied, known as the Indian Ocean Dipole (IOD), was a big player in the severe drought and record hot temperatures last year.

https://www.sciencedaily.com/releases/2020/03/200309135411.htm

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6 minutes ago, knocker said:

Indian Ocean phenomenon spells climate trouble for Australia

https://www.sciencedaily.com/releases/2020/03/200309135411.htm

The article talks about strong IOD causing hot dry conditions in SE Australia. If you look closely at the timing of these events you would see they occur at very low solar minimum. Is it any wonder 1675 is in the middle of the Maunder Minimum. The article is written in such a manner as to blame Climate change and CO2. Sloppy lazy research

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15 minutes ago, jonboy said:

The article talks about strong IOD causing hot dry conditions in SE Australia. If you look closely at the timing of these events you would see they occur at very low solar minimum. Is it any wonder 1675 is in the middle of the Maunder Minimum. The article is written in such a manner as to blame Climate change and CO2. Sloppy lazy research

Well I  assume as you are accusing them of sloppy and lazy research that you have read the paper. I'm afraid I don't have access

Coupling of Indo-Pacific climate variability over the last millennium

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Abstract

The Indian Ocean Dipole (IOD) affects climate and rainfall across the world, and most severely in nations surrounding the Indian Ocean1,2,3,4. The frequency and intensity of positive IOD events increased during the twentieth century5 and may continue to intensify in a warming world6. However, confidence in predictions of future IOD change is limited by known biases in IOD models7 and the lack of information on natural IOD variability before anthropogenic climate change. Here we use precisely dated and highly resolved coral records from the eastern equatorial Indian Ocean, where the signature of IOD variability is strong and unambiguous, to produce a semi-continuous reconstruction of IOD variability that covers five centuries of the last millennium. Our reconstruction demonstrates that extreme positive IOD events were rare before 1960. However, the most extreme event on record (1997) is not unprecedented, because at least one event that was approximately 27 to 42 per cent larger occurred naturally during the seventeenth century. We further show that a persistent, tight coupling existed between the variability of the IOD and the El Niño/Southern Oscillation during the last millennium. Indo-Pacific coupling was characterized by weak interannual variability before approximately 1590, which probably altered teleconnection patterns, and by anomalously strong variability during the seventeenth century, which was associated with societal upheaval in tropical Asia. A tendency towards clustering of positive IOD events is evident in our reconstruction, which—together with the identification of extreme IOD variability and persistent tropical Indo-Pacific climate coupling—may have implications for improving seasonal and decadal predictions and managing the climate risks of future IOD variability.

https://www.nature.com/articles/s41586-020-2084-4

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31 minutes ago, knocker said:

Well I  assume as you are accusing them of sloppy and lazy research that you have read the paper. I'm afraid I don't have access

Coupling of Indo-Pacific climate variability over the last millennium

https://www.nature.com/articles/s41586-020-2084-4

extreme positive IOD events were rare before 1960. They were rare before 1960 because very low solar minimum' were rare. the very positive event of 1913/14 was again at a low solar minimum.  we know the IOD goes through negative and positive phases but it is no coincidence in my opinion that such strongly positive events occur during vey low solar minimum.

You can expect positive events to occur as we go through cycle 25 and given the low base we are coming from I fully expect SE Australia to be in a constant drought flood scenario for at least the next 10/15 years. They need to accept this and manage accordingly

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4 minutes ago, jonboy said:

extreme positive IOD events were rare before 1960. They were rare before 1960 because very low solar minimum' were rare. the very positive event of 1913/14 was again at a low solar minimum.  we know the IOD goes through negative and positive phases but it is no coincidence in my opinion that such strongly positive events occur during vey low solar minimum.

You can expect positive events to occur as we go through cycle 25 and given the low base we are coming from I fully expect SE Australia to be in a constant drought flood scenario for at least the next 10/15 years. They need to accept this and manage accordingly

Perhaps, before describing the work of experts published in one of the most respected scientific journals on the planet "sloppy", you could explain a few things:

1) The mechanism linking solar activity to the IOD.
2) The lack of positive IOD events in previous solar minima (e.g., Dalton).
4) The current positive event, considering there's been numerous similar solar lows that didn't produce them.
3) The significant anomalous positive events during the 90s.
4) The fact that 4 of the 10 largest events were during the last 60 years.

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Tropical climate responses to projected Arctic and Antarctic sea-ice loss

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Arctic and Antarctic sea-ice extent are both projected to dramatically decline over the coming century. The effects of Arctic sea-ice loss are not limited to the northern high latitudes, and reach deep into the tropics. Yet little is known about the effects of future Antarctic sea-ice loss outside of the southern high latitudes. Here, using a fully coupled climate model, we investigate the tropical response to Antarctic sea-ice loss and compare it with the response to Arctic sea-ice loss. We show that Antarctic seaice loss, similar to Arctic sea-ice loss, causes enhanced warming in the eastern equatorial Pacific and an equatorward intensification of the Intertropical Convergence Zone. We demonstrate that Antarctic sea-ice loss causes a mini global warming signal comparable to the one caused by Arctic sea-ice loss, and reminiscent of the response to greenhouse gases. We also show that ocean dynamics are key to capturing the tropical response to sea-ice loss. In short, we find that future Antarctic sea-ice loss will exert a profound influence on the tropics. Combined Arctic and Antarctic sea-ice losses will account for 20–30% of the projected tropical warming and precipitation changes under the high-emissions scenario Representative Concentration Pathway 8.5.

https://www.nature.com/articles/s41561-020-0546-9.epdf?author_access_token=m2Ez4ZueiR8rjNG0e3uGD9RgN0jAjWel9jnR3ZoTv0Nd3Q7P9jiUTjGkDnXAzD5zwpe7dauPgAREv5fZCCcjwxPTFtucn_YUox7KKn9NXV_o83csmblqtaDyXS6PvT_zTmbPerYLHJIQf_7Fm-ECLg%3D%3D

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The Arctic may influence Eurasian extreme weather events in just two to three weeks

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Previous research studies have revealed how rising temperatures and melting ice in the Arctic may impact the rest of Earth's climate over seasons, years and even longer. Now, two researchers from Fudan University in Shanghai, China, are making the argument that the effects may actually be felt in a matter of weeks, but more robust, observational-based analysis is needed to fully understand how quickly Arctic events impact the rest of Earth.

https://phys.org/news/2020-04-arctic-eurasian-extreme-weather-events.html

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Climate-driven megadrought is emerging in western US, says study

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With the western United States and northern Mexico suffering an ever-lengthening string of dry years starting in 2000, scientists have been warning for some time that climate change may be pushing the region toward an extreme long-term drought worse than any in recorded history. A new study says the time has arrived: a megadrought as bad or worse than anything even from known prehistory is very likely in progress, and warming climate is playing a key role. The study, based on modern weather observations, 1,200 years of tree-ring data and dozens of climate models, appears this week in the leading journal Science.

"Earlier studies were largely model projections of the future," said lead author Park Williams, a bioclimatologist at Columbia University's Lamont-Doherty Earth Observatory. "We're no longer looking at projections, but at where we are now. We now have enough observations of current drought and tree-ring records of past drought to say that we're on the same trajectory as the worst prehistoric droughts."

https://www.eurekalert.org/pub_releases/2020-04/eiac-cmi041320.php

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Global increase in major tropical cyclone exceedance probability over the past four decades

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Significance

Tropical cyclones (TCs), and particularly major TCs, pose substantial risk to many regions around the globe. Identifying changes in this risk and determining causal factors for the changes is a critical element for taking steps toward adaptation. Theory and numerical models consistently link increasing TC intensity to a warming world, but confidence in this link is compromised by difficulties in detecting significant intensity trends in observations. These difficulties are largely caused by known heterogeneities in the past instrumental records of TCs. Here we address and reduce these heterogeneities and identify significant global trends in TC intensity over the past four decades. The results should serve to increase confidence in projections of increased TC intensity under continued warming.

Abstract

Theoretical understanding of the thermodynamic controls on tropical cyclone (TC) wind intensity, as well as numerical simulations, implies a positive trend in TC intensity in a warming world. The global instrumental record of TC intensity, however, is known to be heterogeneous in both space and time and is generally unsuitable for global trend analysis. To address this, a homogenized data record based on satellite data was previously created for the period 1982–2009. The 28-y homogenized record exhibited increasing global TC intensity trends, but they were not statistically significant at the 95% confidence level. Based on observed trends in the thermodynamic mean state of the tropical environment during this period, however, it was argued that the 28-y period was likely close to, but shorter than, the time required for a statistically significant positive global TC intensity trend to appear. Here the homogenized global TC intensity record is extended to the 39-y period 1979–2017, and statistically significant (at the 95% confidence level) increases are identified. Increases and trends are found in the exceedance probability and proportion of major (Saffir−Simpson categories 3 to 5) TC intensities, which is consistent with expectations based on theoretical understanding and trends identified in numerical simulations in warming scenarios. Major TCs pose, by far, the greatest threat to lives and property. Between the early and latter halves of the time period, the major TC exceedance probability increases by about 8% per decade, with a 95% CI of 2 to 15% per decade.

https://www.pnas.org/content/early/2020/05/12/1920849117

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A Spatially Variable Time Series of Sea Level Change Due to Artificial Water Impoundment

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Abstract

The artificial impoundment of water behind dams causes global mean sea level (GMSL) to fall as reservoirs fill, but also generates a local rise in sea level due to the increased mass in the reservoir and the crustal deformation this mass induces. To estimate spatiotemporal fluctuations in sea level due to water impoundment, we use a historical data set that includes 6,329 reservoirs completed between 1900 and 2011, as well as projections of 3,565 reservoirs that are expected to be completed by 2040. The GMSL change associated with the historical data (–0.2 mm yr‐1 from 1900 – 2011) is consistent with previous studies, but the temporal and spatial resolution allows for local studies that were not previously possible, revealing that some locations experience a sea level rise of as much as 40 mm over less than a decade. Future construction of reservoirs through ~2040 is projected to cause a GMSL fall whose rate is comparable to that of the last century (–0.3 mm yr‐1), but with a geographic distribution that will be distinct from the last century, including a rise in sea level in more coastal areas. The analysis of expected construction shows that significant impoundment near coastal communities in the coming decades could enhance the flooding risk already heightened by global sea level rise.

Plain Language Summary

Filling a reservoir prevents that water from flowing back to the ocean, thus causing sea level to fall. But sea level does not change by the same amount everywhere: the mass of the water in the reservoir causes sea level to rise in locations near the reservoir, but fall in locations that are farther away. We use databases that include the locations and capacities of reservoirs to estimate how constructing reservoirs has changed sea level, and explore how these changes have varied in space and in time. We find that while constructing reservoirs since 1900 has caused sea level to fall on average, there are some locations that experience a dramatic sea level rise, as much as 40 mm, over a short period of time, usually only a few years. As more reservoirs are built, we expect this trend to continue. In fact, reservoirs that are currently being planned—if completed—will generate a sea level rise of a few millimeters in some low‐lying coastal areas. This rise would be in addition to the rise in sea level from many other known factors.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020EF001497?af=R

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