Saturday, October 25, 2014

New paper explains how Polar Vortex is controlled by natural variability, not CO2

A paper published today in Climate Dynamics finds complex, non-linear, and chaotic interactions of natural gravity waves, the El Nino Southern Oscillation [ENSO], the solar cycle, and the Quasi-Biennial Oscillation [QBO] "combine to affect the polar vortex." The Quasi-Biennial Oscillation [QBO] and ENSO have also been linked to solar activity and may act as potential solar amplification mechanisms which affect the dreaded polar vortex.




Some warmists such as Jennifer Francis and Katherine Hayhoe instead want you to believe that recent record-cold winters due to dips of the polar vortex are your fault, due to your evil CO2 emissions and the CO2 universal control knob of climate. This false assumption has been thoroughly shot down in the peer-reviewed literature by fellow warmists, even including Kevin Trenberth et al. Climate models robustly predict the opposite of fewer jet stream and polar vortex dips due to global warming. 

This new paper provides a start to explain how natural forcings and feedbacks [some of which are linked to solar activity] combine chaotically and unexpectedly with "the opposite sign to the forcing" to govern the polar vortex. The paper also joins others finding links between solar activity and the polar vortex. 

Excerpts:



"The demonstration that the steady state stratospheric response to a forcing may have the opposite sign to the forcing (Sect. 3.1) has important implications for studies of the mechanisms by which external forcings influence the polar vortex—in principle it could be the case that the direct effect of a forcing has the opposite sign to the long-term mean response. As far as we are aware, this possibility has not been considered in any previous studies of the effect on the [polar] vortex of forcings such as the QBO, ENSO and the solar cycle. Feedbacks may greatly modify the response from what is expected based on simple arguments. It also highlights the difficulties of using diagnostics such as composite differences to understand forcing mechanisms, since these may be dominated by the effects of feedback processes (Watson and Gray 2014). [i.e. chaos]
The implication that the extratropical stratospheric response to an external forcing is affected by the climatology may be relevant for understanding non-linearity in the way different forcings combine to affect the polar vortex, such as the suggested non-linear combined influence of the QBO and ENSO (Garfinkel and Hartmann 2007; Wei et al. 2007) and of the QBO and solar cycle (e.g. Labitzke 1987; Matthes et al. 2004). When one forcing affects the background circulation, this would be expected to change the circulation response to other forcings, and this effect may contribute to the reported non-linearities."
Climate Dynamics [full paper open access]

The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode


Peter A. G. Watson and Lesley J. Gray

The response of the wintertime Northern Hemisphere (NH) stratosphere to applied extratropical zonally symmetric zonal torques, simulated by a primitive equation model of the middle atmosphere, is presented. This is relevant to understanding the effect of gravity wave drag (GWD) in models and the influence of natural forcings such as the quasi-biennial oscillation (QBO), El Ninõ-Southern Oscillation (ENSO), solar cycle and volcanic eruptions on the polar vortex. There is a strong feedback due to planetary waves, which approximately cancels the direct effect of the torque on the zonal acceleration in the steady state and leads to an EP flux convergence response above the torque’s location. The residual circulation response is very different to that predicted assuming wave feedbacks are negligible. The results are consistent with the predictions of ray theory, with applied westerly torques increasing the meridional potential vorticity gradient, thus encouraging greater upward planetary wave propagation into the stratosphere. The steady state circulation response to torques applied at high latitudes closely resembles the Northern annular mode (NAM) in perpetual January simulations. This behaviour is analogous to that shown by the Lorenz system and tropospheric models. Imposed westerly high-latitude torques lead counter-intuitively to an easterly zonal mean zonal wind (u¯) response at high latitudes, due to the wave feedbacks. However, in simulations with a seasonal cycle, the feedbacks are qualitatively similar but weaker, and the long-term response is less NAM-like and no longer easterly at high latitudes. This is consistent with ray theory and differences in climatological u¯between the two types of simulations. The response to a tropospheric wave forcing perturbation is also NAM-like. These results suggest that dynamical feedbacks tend to make the long-term NH extratropical stratospheric response to arbitrary external forcings NAM-like, but only if the feedbacks are sufficiently strong. This may explain why the observed polar vortex responses to natural forcings such as the QBO and ENSO are NAM-like [Northern annular mode]. The results imply that wave feedbacks must be understood and accurately modelled in order to understand and predict the influence of GWD and other external forcings on the polar vortex, and that biases in a model’s climatology will cause biases in these feedbacks.

New paper finds why Earth is 2-3C cooler now than in the past, despite the same levels of CO2

A new study finds a
"different pattern of deep ocean circulation was responsible for the elevated temperatures 3 million years ago when the carbon dioxide level in the atmosphere was arguably what it is now and the temperature was 4 degree Fahrenheit higher. They say the formation of the ocean conveyor cooled the earth and created the climate we live in now."
Warmists prefer to claim that since CO2 levels today are about the same as during the Pliocene [5.333 million to 2.58 million years ago] and temperatures were 2-3C higher that we should expect the same 2-3C global warming to be "in the pipeline" in the near future. This new paper, however, finds
"the establishment of the modern deep ocean circulation – the ocean conveyor – about 2.7 million years ago [during the late Pliocene], and not a major change in carbon dioxide concentration in the atmosphere, triggered an expansion of the ice sheets in the Northern Hemisphere”
Therefore, due to increased heat transfer between the Northern and Southern Hemispheres from the establishment of the modern ocean conveyor belts, the oceans and globe have significantly cooled and we should not expect a temperature rise "in the pipeline" of an additional 2-3C for the same levels of CO2 today as were present during the Pliocene [even if one believes the climate is highly sensitive to CO2]. Further, climate models are unable to model or predict ocean oscillations and their complex interactions with other ocean and atmospheric oscillations and subsequent large-scale effects upon climate.

Note also the lack of correlation between temperature and CO2 levels on geologic timescales:


Also note that temperature leads CO2 on long, intermediate, and short-term timescales. The cause does not follow the effect [mathematical proof]. 



Click to enlarge. The ocean conveyor moves heat and water between the hemispheres, along the ocean bottom. It also moves carbon dioxide. Courtesy: NASA.

Click to enlarge. Stella Woodard, postdoctoral researcher in the Department of Marine and Coastal Sciences. Courtesy: Rutgers.

Click to enlarge. Yair Rosenthal, professor of marine and coastal sciences. Courtesy: Rutgers.
Most of the concerns about climate change have focused on the amount of greenhouse gases that have been released into the atmosphere.
But in a new study published in Science, a group of researchers have found that circulation of the ocean plays an equally important role in regulating the earth’s climate.
In their study, the researchers say the major cooling of Earth and continental ice build-up in the Northern Hemisphere 2.7 million years ago coincided with a shift in the circulation of the ocean – which pulls in heat and carbon dioxide in the Atlantic and moves them through the deep ocean from north to south until it’s released in the Pacific.

The ocean conveyor system, scientists believe, changed at the same time as a major expansion in the volume of the glaciers in the northern hemisphere as well as a substantial fall in sea levels. It was the Antarctic ice, they argue, that cut off heat exchange at the ocean's surface and forced it into deep water. They believe this caused global climate change at that time, not carbon dioxide in the atmosphere.
“We argue that it was the establishment of the modern deep ocean circulation – the ocean conveyor – about 2.7 million years ago, and not a major change in carbon dioxide concentration in the atmosphere that triggered an expansion of the ice sheets in the northern hemisphere,” says Stella Woodard, lead author and a post-doctoral researcher in the Department of Marine and Coastal Sciences at Rutgers University. Their findings, based on ocean sediment core samples between 2.5 million to 3.3 million years old, provide scientists with a deeper understanding of the mechanisms of climate change today.
The study shows that changes in heat distribution between the ocean basins is important for understanding future climate change. However, scientists can’t predict precisely what effect the carbon dioxide currently being pulled into the ocean from the atmosphere will have on climate. Still, they argue that since more carbon dioxide has been released in the past 200 years than any recent period in geological history, interactions between carbon dioxide, temperature changes and precipitation, and ocean circulation will result in profound changes.[non-sequitur]

Scientists believe that the different pattern of deep ocean circulation was responsible for the elevated temperatures 3 million years ago when the carbon dioxide level in the atmosphere was arguably what it is now and the temperature was 4 degree Fahrenheit higher. They say the formation of the ocean conveyor cooled the earth and created the climate we live in now.  
“Our study suggests that changes in the storage of heat in the deep ocean could be as important to climate change as other hypotheses – tectonic activity or a drop in the carbon dioxide level – and likely led to one of the major climate transitions of the past 30 million years," says Yair Rosenthal, co-author and professor of marine and coastal sciences at Rutgers
The paper’s co-authors are Woodard,  Rosenthal, Kenneth Miller and James Wright, both professors of earth and planetary sciences at Rutgers; Beverly Chiu, a Rutgers undergraduate majoring in earth and planetary sciences; and  Kira Lawrence, associate professor of geology at Lafayette College in Easton.

Abstract: Earth’s climate underwent a major transition from the warmth of the late Pliocene, when global surface temperatures were ~2-3°C higher than today, to extensive Northern Hemisphere glaciation (NHG) at ~2.73 Ma. We show that North Pacific deep waters were significantly colder (4°C) and likely fresher than North Atlantic deep water prior to the intensification of NHG. At ~2.73 Ma, the Atlantic-Pacific temperature gradient was reduced to < 1°C suggesting the initiation of stronger heat transfer from the North Atlantic to the deep Pacific. We posit that increased glaciation of Antarctica, deduced from the 21 ± 10 m sea-level fall from 3.15-2.75 Ma, and the development of a strong polar halocline, fundamentally altered deep ocean circulation, which enhanced inter-hemispheric heat and salt transport thereby contributing to the NHG.

Antarctic role in Northern Hemisphere glaciation by Stella C. Woodard, Yair Rosenthal, Kenneth G. Miller, James D. Wright, Beverly K. Chiu and Kira T. Lawrence published in Science DOI: 10.1126/science.1255586
Read the abstract and get the paper here.   Rutgers University news release here. 

New paper finds excuse #55 for the 'pause' in global warming: Reduced warming in N. Atlantic subpolar gyre

A paper published today in the Journal of Climate finds, 
"the sea level rise in the North Atlantic subpolar gyre developed at a reduced rate in the 2000s compared to rates in the 1990s" and "the heat content balance ([is assumed] equivalent [to] variations in the sea level)" 
and that this 
"low-frequency variability in the North Atlantic subpolar gyre relates to the propagation of Atlantic meridional overturning circulation (AMOC) variations from the deep-water formation region to mid-latitudes in the North Atlantic, which might have the implications for recent global surface warming hiatus."
Thus, a decline in the rate of heat content and thermosteric sea level rise of the North Atlantic subpolar gyre affected the propagation [speed] of the Atlantic meridional overturning circulation (AMOC) and might be a cause for the "recent global surface warming hiatus."


The paper adds to many others attempting to explain the 18-26 year "pause" or "hiatus" in global warming. 





Climate signals in the mid to high latitude North Atlantic from altimeter observations

Feili Li,1,2 Young-Heon Jo,1,3 Xiao-Hai Yan,1,4 and W. Timothy Liu5
1 College of Earth, Ocean and Environment, University of Delaware, Newark, DE
2 now at Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC
3 now at Department of Oceanography, Pusan National University, Busan, South Korea
4 University of Delaware/Xiamen University Joint Institute of Coastal Research and Management, Newark, DE
5 Jet Propulsion Laboratory 300-323, California Institute of Technology, Pasadena, CA
Abstract
The variability of the sea surface height anomaly (SSHA) in the mid- to high-latitude North Atlantic for the period of 1993 – 2010 was investigated using the Ensemble Empirical Mode Decomposition to identify the dominant timescales. Sea level variations in the North Atlantic subpolar gyre (SPG) are dominated by the annual cycle and the long-term increasing trend. In comparison, the SSHA along the Gulf Stream (GS) is dominated by variability at intra-seasonal and annual timescales. Moreover, the sea level rise in the SPG [North Atlantic subpolar gyre] developed at a reduced rate in the 2000s compared to rates in the 1990s, which was accompanied by rebound in SSHA variability following a period of lower variability in the system. These changes in both apparent trend and low-frequency SSHA oscillations reveal the importance of low-frequency variability in the SPG. To identify the possible contributing factors for these changes, the heat content balance (equivalent variations in the sea level) in the subpolar region was examined. The results indicate that horizontal circulations [ocean oscillations] may primarily contribute to the interannual to decadal variations, while the air-sea heat flux is not negligible at annual timescale. Furthermore, the low-frequency variability in the SPG [North Atlantic subpolar gyre] relates to the propagation of Atlantic meridional overturning circulation (AMOC) variations from the deep-water formation region to mid-latitudes in the North Atlantic, which might have the implications for recent global surface warming hiatus.

Friday, October 24, 2014

Ocean data shows IPCC exaggerates anthropogenic global warming by factor of ~4.6 times

A paper published in Nature Geoscience attempts to explain away Trenberth's "missing heat" as being "within uncertainty" of the dicey ocean heat content data. According to the authors,
"We combine satellite data with ocean measurements to depths of 1,800 m, and show that between January 2001 and December 2010, Earth has been steadily accumulating energy at a rate of 0.50 ± 0.43 Wm−2 (uncertainties at the 90% confidence level). We conclude that energy storage is continuing to increase in the sub-surface ocean."
However, the small "steadily accumulating energy" of only 0.50 W/m2 is far less than even the most conservative estimates from the IPCC AR5 of total anthropogenic radiative forcing. According to the IPCC's "high confidence" estimates, total anthropogenic radiative forcing in 2011 relative to 1750 was 2.29 W/m2 [range 1.13-3.33, at "90% certainty"]. Thus, the ocean data demonstrates Earth is accumulating heat at 4.6 times [2.29/0.5] less than the IPCC central estimate, and 2.3 times less than the IPCC lower-bound estimate. 

Thus, the alleged energy accumulation of "0.50 ± 0.43 Wm−2 (uncertainties at the 90% confidence level)" is not even within the IPCC bounded estimates for energy accumulation, therefore, most of the "missing heat" remains AWOL, or most likely, never existed. 

Further, the fact that Earth has accumulated energy does not imply it must be from anthropogenic sources. Solar amplification mechanisms, including driving of ocean oscillations, cannot be conveniently ruled out as the source or a contributing source. 

In addition, the figures below from the paper show the warming rates of the oceans have generally declined since 1993 and since 2001, opposite of the warmist's claims that more of the "missing heat" has recently decided to hide in the oceans, one of over 50 'excuses' for the 18+ year "pause" of global warming. 

From IPCC latest AR5 report, chart of radiative forcings relative to 1750.














Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty

Nature Geoscience
 
5,
 
110–113
 
 
doi:10.1038/ngeo1375
Received
 
Accepted
 
Published online
 
Global climate change results from a small yet persistent imbalance between the amount of sunlight absorbed by Earth and the thermal radiation emitted back to space1. An apparent inconsistency has been diagnosed between interannual variations in the net radiation imbalance inferred from satellite measurements and upper-ocean heating rate from in situ measurements, and this inconsistency has been interpreted as ‘missing energy’ in the system2. Here we present a revised analysis of net radiation at the top of the atmosphere from satellite data, and we estimate ocean heat content, based on three independent sources. We find that the difference between the heat balance at the top of the atmosphere and upper-ocean heat content change is not statistically significant when accounting for observational uncertainties in ocean measurements3, given transitions in instrumentation and sampling. Furthermore, variability in Earth’s energy imbalance relating to El Niño-Southern Oscillation is found to be consistent within observational uncertainties among the satellite measurements, a reanalysis model simulation and one of the ocean heat content records. We combine satellite data with ocean measurements to depths of 1,800m, and show that between January 2001 and December 2010, Earth has been steadily accumulating energy at a rate of 0.50±0.43Wm−2 (uncertainties at the 90% confidence level). We conclude that energy storage is continuing to increase in the sub-surface ocean.



Thursday, October 23, 2014

UCS climate scientist tells litany of lies denying the 'pause' in global warming satellite data

At the "UCLA Hammer Forum on Climate Change" held tonight, the only speakers were warmists Michael Mann and Brenda Ekwurzel, a senior climate scientist for the Union of Concerned Scientists (UCS). Although audio and video recording was prohibited, my notes on a few of the litany of lies in the presentation by Dr. Ekwurzel are below [I'll post separately on Mann's presentation].

Following a 15 minute presentation each by Mann and Ekwurzel, the audience was allowed to ask questions by writing them down on index cards. No verbal questions were permitted from the audience. My question was the only "skeptical" question from the audience of about 150 mostly elderly academics & a few UCLA students, and was directed to Dr. Ekwurzel by the moderator:
Q: Why does satellite data show that global warming has stopped or "paused" for more than 18 years, despite climate models predicting continued warming from increased CO2?
The UCS chief of climate science education, Dr. Ekwurzel, answered the question by denying that there was any "pause" of global warming, falsely claiming that the reason satellite data shows no warming for the last 18 years is that "things were forgotten when the early satellite data was collected," and that after these "forgotten" things were corrected, the satellite data allegedly shows no pause in warming. She claimed that these "forgotten things" included not distinguishing temperatures collected at night vs. daytime, degradation of the sensors on the satellites, and degradation of satellite orbits. 

This is blatantly false information. The fact is both the RSS and UAH satellite datasets have corrected for all of these not-forgotten things, and after all of these corrections, still show a clear "pause" of zero warming for 18+ years. The satellites are equipped with laboratory-calibrated platinum resistance thermometers, which have demonstrated stability to thousandths of a degree over many years, and which are used to continuously calibrate the satellite instruments once every 8 seconds, and thus provide far more accurate and complete temperature data than surface thermometer data. In addition, there are over 50 papers published in the climate literature acknowledging the "pause" or "hiatus" of global warming and attempting to explain it, but apparently Dr. Ekwurzel hasn't gotten around to reading any of those. As Dr. Judith Curry notes, "pause denial is getting more and more difficult with time."


It was difficult keeping up with the additional litany of misrepresentations from Dr. Ekwurzel's presentation, but here are a few:
  • Said she knew AGW was real when she went on an Arctic expedition and saw an area of open water, which she photographed from a helicopter. The ice-free area was only about 1000 feet in diameter, based upon the size of the ship shown in her picture. This proves nothing, and is certainly not unprecedented or unusual in the Arctic.
  • Claimed there is "strong evidence" that heat waves, drought, extreme precipitation, and floods have increased from AGW. In fact, there is no such evidence, and much opposing evidence.
  • Claimed the California drought is unprecedented and caused by AGW. In fact, California mega-droughts were far worse in the past. 
  • Claimed recent California fires were caused by AGW. The data instead shows a decrease in wildfires.
  • Claimed AGW is causing "higher tree mortality." The data instead shows significant global greening from CO2 and warming. 
  • Claimed California citizens voted to approve California's cap and trade law. In fact, California bill AB 32 was passed by the legislature and never voted on by California citizens. 
  • Claimed CO2 lifetime in atmosphere is 800 years. This is slightly higher than the 14 year lifetime proven by the bomb tests.
  • Claimed CO2 levels with business as usual will double before 2100. At current business as usual rate of increase of ~2 ppm per year, doubling of CO2 would require 200 years. Although the CO2 level data is very slightly exponential, extrapolation of the slight exponential component still places doubling well beyond 2100.
Esteemed Union of Concerned Scientists member Kenji would not be proud of Dr. Ekwurzel's highly misleading presentation.

The presentations were recorded on video by the UCLA Hammer Museum, and hopefully will be posted on the internet soon. 

New paper demonstrates natural variability controls floods and typhoons in Taiwan

A new paper published in Climate of the Past reconstructs climate in Taiwan over the past 1,900 years and finds typhoons & floods were at "normal" levels over the 20th century, and were at much higher levels during the pre-Medieval Warm Period and second half of the Little Ice Age. 

In addition, the paper shows in fig. 9 that ENSO events have been relatively uncommon during the modern era [opposite of alarmist claims], and that sea surface temperatures were warmer during the Medieval Warm Period and pre-Medieval Warm Period than during modern times since 1850. 

The paper corroborates many others demonstrating drought and flooding cycles are controlled by natural variability of ocean oscillations and accumulated solar activity, not CO2 levels. Several papers also find the hydrological cycle linked to solar activity, another of many potential solar amplification mechanisms.


Clim. Past, 10, 1857-1869, 2014
www.clim-past.net/10/1857/2014/
doi:10.5194/cp-10-1857-2014



L.-C. Wang1,2, H. Behling1, T.-Q. Lee3, H.-C. Li4, C.-A. Huh3, L.-J. Shiau5, and Y.-P. Chang6
1Department of Palynology and Climate Dynamics, Albrecht-von-Haller Institute for Plant Sciences, University of Göttingen, 37073 Göttingen, Germany
2Collection Management Department, National Taiwan Museum, Taipei 100, Taiwan
3Institute of Earth Sciences, Academia Sinica, Taipei 128, Taiwan
4Department of Geosciences, National Taiwan University, Taipei 106, Taiwan
5Institute of Applied Geosciences, National Taiwan Ocean University, Keelung 202, Taiwan
6Department of Oceanography, National Sun Yat-sen University, Kaohsiung 804, Taiwan

Abstract. We reconstructed paleoenvironmental changes from a sediment archive of a lake in the floodplain of the Ilan Plain of NE Taiwan on multi-decadal resolution for the last ca. 1900 years. On the basis of pollen and diatom records, we evaluated past floods, typhoons, and agricultural activities in this area which are sensitive to the hydrological conditions in the western Pacific. Considering the high sedimentation rates with low microfossil preservations in our sedimentary record, multiple flood events were. identified during the period AD 100–1400. During the Little Ice Age phase 1 (LIA 1 – AD 1400–1620), the abundant occurrences of wetland plant (Cyperaceae) and diatom frustules imply less flood events under stable climate conditions in this period. Between AD 500 and 700 and the Little Ice Age phase 2 (LIA 2 – AD 1630–1850), the frequent typhoons were inferred by coarse sediments and planktonic diatoms, which represented more dynamical climate conditions than in the LIA 1. By comparing our results with the reconstructed changes in tropical hydrological conditions, we suggested that the local hydrology in NE Taiwan is strongly influenced by typhoon-triggered heavy rainfalls, which could be influenced by the variation of global temperature, the expansion of the Pacific warm pool, and the intensification of El Niño–Southern Oscillation (ENSO) events.

New paper finds cooling, not warming, of mid- to upper troposphere increases likelihood of tropical cyclones

A paper published today in the Journal of Climate finds that cooling, not warming, of the mid- to upper troposphere increases the development of tropical cyclones. The mid- to upper troposphere mythical "hot spot" is predicted to warm the most from AGW, but despite millions of weather balloon and satellite measurements, has not been found in observations. Thus, if the mid- to upper troposphere missing "hot spot" ever does form, this paper implies that the probability of tropical cyclones would decrease, not increase as claimed by alarmists. 

In addition, global warming decreases the temperature gradients between the poles and the equator. Since temperature gradients drive all "extreme weather," global warming tends to decrease "extreme weather," not increase as claimed by alarmists.

The paper thus corroborates many others finding that if global warming resumes, it is expected to decrease tropical cyclones and hurricanes in the future. 

Note the paper refers to changing the "parameterized convection" in the climate model, which means that the model cannot directly simulate the physics of convection [due to low resolution] and thus uses fudge factors or "parameterizations" to simulate real convection, as do all IPCC climate models. Here's why and here.


Sensitivity of Tropical Cyclones to Parameterized Convection in the NASA GEOS5 Model

Young-Kwon Lim,1,2 Siegfried D. Schubert,1 Oreste Reale,1,3 Myong-In Lee,5 Andrea M. Molod,1,4 and Max J. Suarez1,3
1 Bldg. 33, code 610.1, 8800 Greenbelt Rd., Global Modeling and Assimilation Office, NASA/GSFC, Greenbelt, Maryland, 20771
2 Goddard Earth Sciences Technology and Research, I. M. Systems Group
3 Goddard Earth Sciences Technology and Research, Universities Space Research Association (USRA)
4 ESSIC, University of Maryland, College Park, Maryland
5 Ulsan Institute of Science and Technology (UNIST), Ulsan, South Korea
Abstract
The sensitivity of tropical cyclones (TCs) to changes in parameterized convection is investigated to improve the simulation of TCs in the North Atlantic. Specifically, the impact of reducing the influence of the Relaxed Arakawa-Schubert (RAS) scheme-based parameterized convection is explored using the Goddard Earth Observing System version5 (GEOS5) model at 0.25° horizontal grid spacing. The years 2005 and 2006 characterized by very active and inactive hurricane seasons, respectively, are selected for simulation.
A reduction in parameterized deep convection results in an increase in TC activity (e.g., TC number and longer life cycle) to more realistic levels compared to the baseline control configuration. The vertical and horizontal structure of the strongest simulated hurricane shows the maximum wind speed greater than 60 ms-1 and the minimum sea level pressure reaching ~940mb, which are never achieved by the control configuration. The radius of the maximum wind of ~50km, the location of the warm core exceeding 10°C, and the horizontal compactness of the hurricane center are all quite realistic without any negatively affecting the atmospheric mean state.
This study reveals that an increase in the threshold of minimum entrainment suppresses parameterized deep convection by entraining more dry air into the typical plume. This leads to cooling and drying at the mid- to upper-troposphere, along with the positive latent heat flux and moistening in the lower-troposphere. The resulting increase in conditional instability provides an environment that is more conducive to TC vortex development and upward moisture flux convergence by dynamically resolved moist convection, thereby increasing TC activity.

Related: Why the AGW "Hot Spot" Won't Happen

New paper demonstrates droughts are controlled by natural variability, not man-made CO2

A paper published today in Palaeogeography, Palaeoclimatology, Palaeoecology finds drought in North China is linked to cycles of sea surface temperatures in the tropical Indian-Pacific Ocean and the East Asian summer monsoon (EASM). In turn, sea surface temperatures are linked to natural ocean oscillations and cumulative solar activity, and both the East Asian summer monsoon (EASM) and ocean oscillations have been linked to solar activity as a driver.

The paper also shows the North China drought from 1827-1850 (during the Little Ice Age) was more severe than recent drought 1984-2012 and that drought conditions have returned to the average range since 2012.  

In addition, global droughts have decreased despite a steady rise of CO2 levels:



These findings thus clearly demonstrate drought cycles are controlled by natural variability of ocean oscillations and accumulated solar activity, not man-made CO2. Several other papers also find the hydrological cycle linked to solar activity, another of many potential solar amplification mechanisms.

PDSI is Palmer Drought Severity Index, low values are associated with severe drought
Reconstructed drought periods shown in brown, wet periods shown in green, intermediate periods in white

Highlights

Temperature induced moisture stress limits the tree growth in North China.
The PDSI reconstruction since 1767 AD is regionally representative.
The reconstruction exhibits a significant drying trend since the mid- 1960s.
Drought in North China is linked to the SST in tropical Indian-Pacific Ocean.

Abstract

Using tree-ring data from the northernmost marginal area of the East Asian summer monsoon (EASM) in North China, May–July mean Palmer drought severity index (PDSI) was reconstructed back to 1767 AD. The reconstruction captured 52.8% of the variance over the calibration period from 1945 to 2005 AD and showed pronounced pluvial periods during 1850–1905, 1803–1811 and 1940–1961 and dry periods during 1814–1844, 1916–1932 and 1984–2012. These anomalous periods have previously been reported in other parts of North China. Spatial correlation analyses and comparisons with other hydroclimatic indices in North China indicated that our new PDSI reconstruction could represent spatial and temporal drought variability in this region well. Our work also suggested that the drying tendency currently observed in the northern part of North China (including the study area) is consistent with the weakening of the EASM. Meanwhile the drying trend was seemingly restrained at present in the southern part of North China. Spatial correlation patterns with global sea surface temperature (SST) indicated that the regional hydroclimatic variability in North China was tightly linked to SST over the joining area of Asia and Indian-Pacific Ocean (AIPO), especially over the tropical western Pacific. When SST from prior November to current July (NJ-SST) in the AIPO area was anomalously high (low), the thermal contrast between Asian land and ocean was weakened (strengthened), and the EASM was correspondingly weakened (strengthened), thereby causing droughts (pluvials) in North China. The results of this study do not only provide useful information for assessing the long-term climate change in North China, but also suggest that abnormal variability in NJ-SST over the AIPO area could be used to forecast hydroclimatic conditions in north China.