Skeptic Papers 2019 (3)

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Climate Model Unreliability/Biases/Errors and the Pause

Tapiador et al., 2019     Uncertainties in modeling persist for large parts of the world, suggesting models still limited to the research realm. … It turns out that both GCMs and RCMs [global/regional climate models] appear still limited to provide practical estimates of the world climates even for present climate conditions.  … The results show that there are significant mismatches between the models and the reference data in, for instance, the case of Europe. …  In Equatorial Africa, the RCMs show a surprising lack of capability. The simulations for the whole continent, which include a different number of models and a different domain, improve very slightly. … These results suggest that both GCMs and the RCMs are still too limited to extract definite estimates of the world climates, even for present climate conditions. Moreover, a closer view of the agreement between modeled and observed precipitation in South and Central America, Asia, Australasia and the Arctic raises serious doubts about whether or not such estimates can be used in practice.
Crawford et al., 2019     We have developed ensembles from 34 CMIP5 GCMs using six diverse approaches, including random forest, support vector regression, neural networks, linear regression, and weighted k-nearest neighbors, and compared the performance of the ensembles with each other and the individual GCMs using a robust set of metrics and nonparametric tests. For temperature, random forest outperforms all other ensembles and the best-performing GCM by a statistically significant margin and is able to simulate temporal and spatial patterns in temperature well. None of the ensembles are able to adequately simulate observed precipitation patterns in the study area, likely due to spatial differences in precipitation drivers in the region, as well as the coarseness of the dataset itself.
Liu et al., 2019     Here we provide an observational assessment of rainfall interactions mechanisms (informed by directional transfer of information entropy) that regulate Sahel rainfall. We quantitatively demonstrate that (1) sea surface temperature over the Gulf of Guinea controls moisture advection and transport to the West Sahel region and (2) strong bidirectional interactions exist between local vegetation dynamics and rainfall patterns. Then we assess the directional interaction patterns from nine state‐of‐the‐art Earth System Models (ESMs). We find that most ESMs are able to represent either the unidirectional control of sea surface temperature on precipitation or the bidirectional interaction between vegetation and precipitation. However, none of the ESMs [System Models] represents both interactive patterns. The GFDL and IPSL‐CM5A‐LR models successfully reproduced observed patterns over ~50% of the West Sahel region but were not accurate in reproducing observed precipitation regional trends or interannual variation. We propose that the directional information transfer is a powerful mechanistic benchmark to assess model fidelity at the process level.
Williams et al., 2019     The hiatus in global warming is manifest in several global datasets in the decadal period 2002–2013. … During the more recent hiatus, lightning observations from the Lightning Imaging Sensor in space show no trend in flash rate. Surface-based, radiosonde-based and satellite-based estimates of global temperature have all been examined to support the veracity of the hiatus in global warming over the time interval of the satellite-based lightning record.
He and Yang, 2019     However, three combined gridded observational datasets, four reanalysis datasets, and most of the CMIP5 models cannot capture extreme precipitation exceeding 150 mm day−1, and all underestimate extreme precipitation frequency. The observed spatial distribution of extreme precipitation exhibits two maximum centers, located over the lower-middle reach of Yangtze River basin and the deep South China region, respectively. Combined gridded observations and JRA-55 capture these two centers, but ERA-Interim, MERRA, and CFSR and almost all CMIP5 models fail to capture them. The percentage of extreme rainfall in the total rainfall amount is generally underestimated by 25%–75% in all CMIP5 models.
Bishop et al., 2019    Atmospheric models forced by observed SSTs and fully coupled models forced by historical anthropogenic forcing do not robustly simulate twentieth-century fall wetting in the SE-Gulf. SST-forced atmospheric models do simulate an intensified anticyclonic low-level circulation around the NASH, but the modeled intensification occurred farther west than observed. CMIP5 analyses suggest an increased likelihood of positive SE-Gulf fall precipitation trends given historical and future GHG forcing. Nevertheless, individual model simulations (both SST forced and fully coupled) only very rarely produce the observed magnitude of the SE-Gulf fall precipitation trend.
Yu, 2019      Given the large uncertainties in surface flux estimates in the tropical and subtropical ocean, it is not a surprise that the surface energy and freshwater budgets determined by the mean Qnet [energy] product differ considerably from those determined by the E − P product. The surface energy budget ranges from a significant ocean heat deficit of 16 W m−2 by JRA-55 to a significant ocean heat gain of 25 W m−2 by OAFlux-1×1. … The accuracy requirement for Qnet [energy] is 10 W m−2 for flux applications on monthly to seasonal timescales (WCRP 1989, Webster & Lukas 1992, WGASF 2000, Weller et al. 2004, Bradley & Fairall 2007). If the goal is to detect long-term trends from a background of natural variability, then the accuracy requirement is at least one order of magnitude higher, at O(1 W m−2) for Qnet [energy] and O(1 cm y−1) for FW [freshwater]. Observationally based estimates show that the ocean has amassed more than 3 × 1023 J of energy since 1960, which corresponds to a net heating of 0.5–1 W m−2 over the global surface (Hansen et al. 2005, Levitus et al. 2005, Lyman & Johnson 2013, Allan et al. 2014, Cheng et al. 2017). All parameterization-based flux products have difficulty closing the ocean heat budget within this limit. Ship-based climatological analyses show mean heat gains by the ocean of approximately 30 W m−2 or greater (Isemer et al. 1989, Large et al. 1997, Josey et al. 1999), and satellite-based products have a similar degree of imbalance (Liu et al. 2017).

Li et al., 2019     Global warming stalled or paused for the period 1998–2012, as claimed by the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) (IPCC, 2013). However, the early drafts of IPCC AR5 have no detailed explanation for this “hiatus” since 111 of 114 climate models in the CMIP5 earth system model did not verify this phenomenon. … In 2017, after a wave of scientific publications and public debate, the climate models as reported in IPCC remain debates, including definitions of “hiatus” and datasets (Medhaug et al., 2017)…. The slowdown in global warming since 1998, often termed the global warming hiatus. Reconciling the “hiatus” is a main focus in the 2013 climate change conference. Accurately characterizing the spatiotemporal trends in surface air temperature (SAT) is helps to better understand the “hiatus” during the period. This article presents a satellite-based regional warming simulation to diagnose the “hiatus” for 2001–2015 in China. Results show that the rapid warming is mainly in western and southern China, such as Yunnan (mean ± standard deviation: 0.39 ± 0.26 °C (10 yr)−1 ), Tibet (0.22 ± 0.25 °C (10 yr)−1), Taiwan (0.21 ± 0.25 °C (10 yr)−1), and Sichuan (0.19± 0.25 °C (10 yr)−1). On the contrary, there is a cooling trend by 0.29 ± 0.26 °C (10 yr)−1 in northern China during the recent 15 yr, where a warming rate about 0.38 ± 0.11 °C (10 yr)−1 happened for 1960–2000. Overall, satellite simulation shows that the warming rate is reduced to −0.02 °C (10 yr)−1. The changes in underlying surface, Earth’s orbit, solar radiation and atmospheric counter radiation (USEOSRACR) cause China’s temperature rise about 0.02 °C (10 yr)−1. A combination of greenhouse gases (GHGs) and other natural forcing (ONAT, predominately volcanic activity, and atmosphere and ocean circulation) explain another part of temperature trend by approximately −0.04 °C (10 yr)−1. We conclude that there is a regional warming hiatus, a pause or a slowdown in China, and imply that GHGs-induced warming is suppressed by ONAT in the early 21st century.

Williamson and Sansom, 2019   The arguments in this paper make it very clear that strong scientific judgement is implied when linking models to reality, particularly when claiming that a linear relationship between quantities across models indicates a physical relationship. Data mining for constraints may very well lead to a multiple testing problem. A simple numerical experiment can be used to illustrate the point. Generating 430 000 (normal) random numbers and stacking these into a matrix with 43 rows, generates a pseudo ensemble with 43 members and with no physical links between the 10 000 outputs. Looking at the maximum absolute correlation between outputs across the ensemble will usually return correlations between 0.7 and 0.85, well above the threshold for relationships for an emergent constraint. To base the strong beliefs required to take this relationship into the real world (in the way we have made clear), on only the discovery of a large correlation cannot be justified. For that reason, even specifying a low confidence in the constraint through our guided framework would still be inappropriate.
Chen et al., 2019     23 out of the 30 CMIP5 models overestimate the standard deviation of the SLP anomalies north of 20°N. … In particular, 20 out of the 30 models produce stronger SLP anomalies over the North Atlantic (Fig. 4b). By contrast, the CESM1-WACCM and HadGEM2-ES obviously produce a much weaker SLP anomalies over the North Atlantic (Fig. 4b). … The models simulating a stronger spring SLP anomalies over the North Pacifc and North Atlantic do not necessarily have a stronger SLP climatology. Specifcally, the correlation coefficients between the two quantities in Fig. 5a, c are only 0.16 and 0.03, respectively. … Above results suggest that majority of the 30 CMIP5 models cannot realistically reproduce the observed dominant spectral peak of the spring AO index. …  In region B, the MME reproduces weaker positive air temperature anomalies compared to that in the observation (Fig. 10b). This is related to the fact that 26 out of the 30 CMIP5 models simulate a weaker positive ZM air temperature anomaly. …  Out of the 30 models, 28 CMIP5 models produce larger percent variances of the frst EOF mode than that in the observation.
Connolly et al., 2019     Observed changes in Northern Hemisphere snow cover from satellite records were compared to those predicted by all available Coupled Model Intercomparison Project Phase 5 (“CMIP5”) climate models over the duration of the satellite’s records, i.e., 1967–2018. A total of 196 climate model runs were analyzed (taken from 24 climate models). Separate analyses were conducted for the annual averages and for each of the seasons (winter, spring, summer, and autumn/fall). A longer record (1922–2018) for the spring season which combines ground-based measurements with satellite measurements was also compared to the model outputs. The climate models were found to poorly explain the observed trends. While the models suggest snow cover should have steadily decreased for all four seasons, only spring and summer exhibited a long-term decrease, and the pattern of the observed decreases for these seasons was quite different from the modelled predictions. Moreover, the observed trends for autumn and winter suggest a long-term increase, although these trends were not statistically significant.

Xuejin et al., 2019     Almost half of snow gauge stations over China shows increases in the snow-cover days.

Urban Heat Island: Raising Surface Temperatures Artificially

Wen-qian et al., 2019     Based on an in-homogeneity adjusted dataset of the monthly mean temperature, minimum and maximum temperature, this paper analyzes the temporal characteristics of Urban Heat Island (UHI) intensity at Wuhan Station, and its impact on the long-term trend of surface air temperature change recorded during 1961-2015 by using an urban-rural method. Results show that UHI effect is obvious near Wuhan Station in the past 55 years, especially for minimum temperature. The strongest UHI intensity occurs in summer and the weakest in winter. For the period 1961-2004, UHI intensity undergoes a significant increase near the urban station, with the increase especially large for the period 1988-2004, but a significant decrease is registered for the last 10 years, with the decrease in minimum temperature more significant than that of maximum temperature. The annual mean urban warming and its contribution to overall warming are 0.18°C/10yr and 48.8% respectively for the period 1961-2015, with a more significant and larger urbanization effect seen in Tmin than Tmax. A large proportion warming, about half of the overall increase in annual mean temperature, as observed at the urban station, thus can be attributed to the rapid urbanization in the past half a century. … Zhou et al.[9] found that the contribution of urban warming to the overall warming in the northern China region was 37.9% during 1961-2000, and it even reaches 71% at Beijing station over the same period (Chu et al.[17]); Urbanization-induced SAT trend reaches 0.19°C/10yr during 1962-2009 for Shijiazhuang station, accounting for 68% of all warming trend (Bian et al.[18]). … Chen et al.[20] studied the UHI change trend for Wuhan station from 1960 to 2005, and found that the annual mean urban warming and contribution rate reached 0.235°C/10yr and 60.4% respectively.
Yao et al., 2019     In this study, Moderate resolution imaging spectroradiometer (MODIS) land cover, land surface temperature (LST) and enhanced vegetation index (EVI) data were used to investigate the trends of surface urban heat island intensity (SUHII, urban LST minus rural LST) and their relations with vegetation in 397 global big cities during 2001–2017. Major findings include: (1) annual daytime and nighttime SUHII [surface urban heat island intensity] increased significantly (p < 0.05, Mann-Kendall trend test) in 42.1% and 30.5% cities, respectively; (2) the daytime SUHII in the growing season was significantly and positively correlated with rural EVI in 58.9% cities. … Surface urban heat island (SUHI) refers to higher land surface temperature (LST) in urban than in rural areas. The increased SUHI intensity (SUHII, urban LST minus rural) was mainly attributed to increased anthropogenic heat emission and built-up areas, and reductions in vegetation in urban areas in the literature. However, this study showed that the increased vegetation (i.e. greening) in rural areas was a significant and widespread driver for the increased daytime SUHII around the world during 2001–2017.
Leeper et al., 2019     These results suggest that small-scale urban encroachment within 50 meters of a station can have important impacts on daily temperature extrema (maximum and minimum) with the magnitude of these differences dependent upon prevailing environmental conditions and sensing technology. … As expected, temperature observations were warmest for the site closest to the built environment with an average temperature difference of 0.31 and 0.24 °C for aspirated and unaspirated sensors respectively. Mean aspirated temperature differences were greater during the evening (0.47 °C) than day (0.16 °C).
Goddard and Tett, 2019     This study aims to estimate the affect of urbanisation on daily maximum and minimum temperatures in the United Kingdom. … For an urban fraction of 1.0, the daily minimum 2‐m temperature was estimated to increase by 1.90 ± 0.88 K while the daily maximum temperature was not significantly affected by urbanisation. This result was then applied to the whole United Kingdom with a maximum T min urban heat island intensity (UHII) of about 1.7K in London and with many UK cities having T min UHIIs above one degree. … This paper finds through the method of observation minus reanalysis that urbanisation has significantly increased the daily minimum 2m temperature in the United Kingdom by up to 1.70 K. … Yan et al. (2010) concluded a large impact of urbanisation up to 0.54 K/decade on local temperature series in Beijing.

Failing Renewable Energy, Climate Policies

Pereira et al., 2019   [D]oubt has been cast on the much-vaunted advantages of renewables due to some of their characteristics, such as availability, security and affordability. In fact, growth in the installed capacity of renewable energy has increased electricity prices, which raises the question of how households have withstood the cost of energy transition. This paper proves that both income and risk of household poverty are directly linked with renewable energies, in both the short- and long-run. The energy transition to renewables has had negative consequences for households. … The shift from fossil fuels to RES [renewable energy sources] in electricity generation systems, has virtually doubled the price of electricity, with this increase being split between the cost of generation and RES surcharges.

Pendrill et al., 2019     In total, the share of deforestation attributed to exports was greatest for crops (40%), with some—palm oil, soybeans, tree nuts and other crops—primarily destined for export (63–77%). … The largest export flows went from early- and latet-ransition countries to post-transition countries, and the exported deforestation from pretransition countries was primarily consumed in post-transition countries in Europe.
Pendrill et al., 2019     Deforestation, the second largest source of anthropogenic greenhouse gas emissions, is largely driven by expanding forestry and agriculture. …. Similarly, deforestation emissions constitute a substantial share (˜15%) of the total carbon footprint of food consumption in EU countries. This highlights the need for consumption-based accounts to include emissions from deforestation, and for the implementation of policy measures that cross these international supply-chains if deforestation emissions are to be effectively reduced.
(press release     A sixth of all emissions resulting from the typical diet of an EU citizen can be directly linked to deforestation of tropical forests.  “In effect, you could say that the EU imports large amounts of deforestation every year. If the EU really wants to achieve its climate goals, it must set harder environmental demands on those who export food to the EU,” says Martin Persson from Chalmers, one of the researchers behind the studies. The studies indicate that, although there is a big variation between different EU countries, on average a sixth of the emissions from a typical EU diet can be directly traced back to deforestation in the tropics. Emissions from imports are also high when compared with domestic agricultural emissions. For several EU countries, import emissions connected to deforestation are equivalent to more than half of the emissions from their own, national agricultural production.
Greenstone and Nath, 2019     [R]enewable power plants require ample physical space, are often geographically dispersed, and are frequently located away from population centers, all of which raises transmission costs above those of fossil fuel plants. … [REM-driven] increases in renewable energy penetration can also raise total energy system costs by prematurely displacing existing productive capacity, especially in a period of flat or declining electricity consumption. Adding new renewable installations, along with associated flexibly dispatchable capacity, to a mature grid infrastructure may create a glut of installed capacity that renders some existing baseload generation unnecessary. The costs of these ‘stranded assets’ do not disappear and are borne by some combination of distribution companies, generators, and ratepayers. Thus, the early retirement or decreased utilization of such plants can cause retail electricity rates to rise even while near zero marginal cost renewables are pushing down prices in the wholesale market. … Intermittent wind and solar cannot stand on their own. They must have some form of back-up power, from reliable coal, natural gas, nuclear units, storage capability from hydroelectric facilities, and/or batteries. Batteries of the size and scope needed for 100-percent renewables are unproven and not cost effective. Even if a 100 percent renewable future were feasible, the land requirements and costs of transitioning would be enormous and would require subsidies to ease the electricity price increases that would result.
Nathaniel and Iheonu, 2019     We examined the role of renewable and non-renewable energy consumption on CO2 emissions in Africa. … Renewable energy inhibits CO2 emissions insignificantly in Africa.
Padoan et al., 2019     The rapid increase in the photovoltaic power installed worldwide will cause over the next few decades a dramatic increase in the volume of end-of-life photovoltaic panels. In accordance with the analysis presented in this article, peaks for dismissal of PV panels are expected to occur around the years 2036 and 2045. The improper disposal of these waste fluxes could cause harmful effects to human health and to economy of the manufacture sector by the dispersion of toxic elements and loss of valuable material resources including rare metals, respectively.
Liu et al., 2019     Over the past three decades, China has witnessed spectacular economic growth. However, behind this economic success, the country also faces serious challenges, including pressures to reduce emissions and to address imbalances in its growth. Increasing attention is thus being paid to the task of exploring the relationship between income inequality and CO2 emissions. … China’s energy consumption is dominated by coal, which accounted for 63.7% of the country’s total energy consumption in 2015—China is responsible for more than 50% of the world’s coal consumption. By 2030, China’s CO2 emissions will be equivalent to the rest of the world’s total emissions. … [W]e investigated how the level of income distribution within 30 Chinese provinces influenced that province’s CO2 emissions, using panel data from 1996 to 2014 to estimate both the Gini coefficient and Global Moran’s I. The empirical results show that income growth increased China’s CO2 emissions during the study period, but that an inverted U-shaped relationship existed between income and emissions, thereby confirming the Environmental Kuznets Curve hypothesis. The continuously widening income gap, and especially the uneven spatial distribution of income, can thus be expected to deteriorate environmental quality and increase CO2 emissions. The effect of the self-reinforcing agglomeration of income on emissions was clearly evident.

Wind Power Harming The Environment, Biosphere

Frondel et al., 2019     Given the rapid expansion of wind power capacities in Germany, this paper estimates the effects of wind turbines on house prices using real estate price data from Germany’s leading online broker. Employing a hedonic price model whose specification is informed by machine learning techniques, our methodological approach provides insights into the sources of heterogeneity in treatment effects. We estimate an average treatment effect (ATE) of up to -7.1% for houses within a one-kilometer radius of a wind turbine, an effect that fades to zero at a distance of 8 to 9 km. …  While the prices of houses close to urban environments are not affected by nearby windmills, houses in rural areas suffer from remarkable devaluation. This effect is even more pronounced for old buildings built prior to 1949, whose asking prices decrease by up to 23%. Our findings can be explained by differences in the appearance of the landscape and preferences of the local population. While the urban population is accustomed to living in an industrialized and dynamic environment, inhabitants of rural areas may lose the impression of pristine nature and tranquility when noise, rotation, and shadow flickers appear. Altogether, our results illustrate that while electricity generation via wind turbines may have global benefits, these are accompanied by substantial local externalities and environmental costs, primarily borne by rural communities close to wind turbines.
Xirouchakis et al., 2019     [T]he environmental impact of commercial wind power production on biodiversity has proved to be substantial [3–7]. Wildlife is affected by wind power production through habitat loss, disturbance and displacement and above all by increased collision risk with wind turbines [8–10]. Bird fatalities due to collision with wind turbines have been the most prominent and frequently identified environmental drawback of wind energy development. Bird casualties from collisions can reach up to 40 deaths per turbine per year [11] with large raptors suffering the greatest toll. … We evaluated the consequences of wind farm development on the griffon vulture (Gyps fulvus) which was regarded as a suitable model species. Griffons are among the most collision-prone large soaring raptors and perhaps the most frequent victims of turbine blades in the Mediterranean region, i.e. up to 1.88 individuals/ turbine/ year [8]. Furthermore, assuming that the most crucial factor in minimizing the negative impact of wind farms on wildlife should be proper siting, we tried to estimate the potential collision mortality of the species by taking into account the existing and all planned wind energy projects on Crete. … Crete holds the last healthy population in the country (ca. 1000 individuals) which constitutes the largest indigenous insular population worldwide. … The model predicted that 39% of the griffon colonies which were occupied by more than 15 individuals would account for 62% of the wind farms and vulture interactions and would suffer 65% of the expected mortalities. The overall collision mortality rate was estimated at 0.03 vultures/wind turbine/year producing an annual loss ranging from 3.7% to 11% of the species population. More specifically a total of 990 individuals were estimated to be at threat of striking with turbine blades. The scenario #1 predicted a mean annual mortality of 1.49 ± 1.12 individuals (range = 0.18–4.98) per colony, whereas the overall annual fatality was anticipated at 83.5 griffons.
Marques et al., 2019     We present evidence that the impacts of wind energy industry on soaring birds are greater than previously acknowledged. In addition to the commonly reported fatalities, the avoidance of turbines by soaring birds causes habitat losses in their movement corridors. … Our findings indicate that the negative effects of wind-power developments on soaring birds may be far more extensive than the commonly reported mortality caused by collision (Marques et al., 2014). Avoidance behaviour may suggest that soaring birds, as well as other birds, are partly able to cope with the existence of wind turbines (Marques et al., 2014). However, our results make clear that this is a simplistic interpretation and may lead to the underestimation of the real impacts of wind-power generation. We recommend that the authorities responsible for wildlife protection and wind industry regulations recognize the loss of aerial habitat caused by wind turbines and the potential associated negative impacts on soaring birds.

Elevated CO2: Greens Planet, Higher Crop Yields

Winkler et al., 2019     Historical increase of atmospheric CO2 concentration, from 280 to current 400 ppm, has resulted in enhanced GPP [gross primary production/greening] due to its radiative and physiological effects, which is indirectly evident in amplified seasonal swings of atmospheric CO2 concentration and large scale increase in summer time green leaf area. Thus, these observables, expressed as sensitivities to ambient CO2 concentration, might serve as predictors of changes in GPP and help to reduce uncertainty in multimodel projections of terrestrial carbon cycle entities. This study is focused on the northern high latitudes (NHL, north of 60°N) where significant and linked changes in climate and vegetation have been observed in the past 3–4 decades: 52% of the vegetated lands show statistically significant greening trends over the 36-year record of satellite observations (1981–2016, Methods), while only 12% show browning trends, mostly in the North American boreal forests due to disturbances. … Here, we apply the concept of Emergent Constraints (EC) to reduce uncertainty in multi-model projections of GPP using historical simulations and satellite observations of LAI focusing on NHL. We find that the EC estimate [of the effect of CO2 on greening/GPP] is 60% larger than the commonly accepted multi-model mean value, in line with a recent study that assessed the impact of physiological effects of higher CO2 concentration on GPP of northern hemispheric extra-tropical vegetation. Detailed independent analyses of insitu CO2 measurements and atmospheric inversions imbue confidence in our conclusions. Our central finding is, the effect of ambient CO2 concentration on terrestrial photosynthesis is larger than previously thought, and thus, has important implications for future carbon cycle and climate.

Qiao et al., 2019     Maize had 25% yield increase under elevated temperature (eT). Soybean had 31% yield increase under elevated CO2 (eCO2) with eT. Elevated temperature with and without eCO2 increased grain oil concentrations.
Brandt et al., 2019     Recent Earth observation studies find a greening of the Earth and in particular in global drylands, which is commonly interpreted as a global increase in net primary production and has been attributed to climate change. Although changes in rainfall, fire regimes, elevated temperatures, atmospheric CO2 and nitrogen depositions are suggested explanations, only few studies provide quantitative evidence on both the biophysical processes (changes in vegetation cover, structure and composition) and controlling factors of long-term dryland vegetation trends.
Cernusak et al., 2019     Human-caused CO2 emissions over the past century have caused the climate of the Earth to warm and have directly impacted on the functioning of terrestrial plants. We examine the global response of terrestrial gross primary production (GPP) to the historic change in atmospheric CO2. The GPP of the terrestrial biosphere has increased steadily, keeping pace remarkably in proportion to the rise in atmospheric CO2. Water-use efficiency, namely the ratio of CO2 uptake by photosynthesis to water loss by transpiration, has increased as a direct leaf-level effect of rising CO2. This has allowed an increase in global leaf area, which has conspired with stimulation of photosynthesis per unit leaf area to produce a maximal response of the terrestrial biosphere to rising atmospheric CO2 and contemporary climate change.
Wang et al., 2019     Changes in Vegetation Greenness in the Upper and Middle Reaches of the Yellow River Basin over 2000–2015 … In this study, the vegetation dynamic characteristics were analyzed for unconverted forestland, shrubland, grassland, cropland, and converted forestland, shrubland, and grassland from cropland over 2000–2015 in the upper and middle reaches of the Yellow River. … The results obtained were as follows: (1) Vegetation greening was remarkable in the entire study region (0.036 yr−1). … Overall greening trend in the upper and middle reaches of the Yellow River indicated great achievements have been obtained since the implementation of the GTGP. Vegetation restoration exerted stronger influences on converted types from cropland than unconverted types. In the future, approximately 73.1% of the study region is expected to continue increasing [greening].

 

Zhang et al., 201      While summer GST [ground surface temperature] had a somewhat consistently positive correlation with tree growth, winter GST has shifted from a negative to a strongly positive correlation with growth in the last decade, coincidental with a sharp increase in winter GST since 2004. Winter GST is also strongly correlated with the rapidly thawing permafrost dynamics. Overall, our results suggest a link between recent changes in the permafrost and shifts in climategrowth correlations for one of the main boreal tree species. As a result, L. gmelinii has experienced an important increase in radial growth that may indicate that, unlike what has been reported for other boreal species, it may temporally benefit from warming climate in the continuous permafrost region of the Asian boreal forests.
Oliveira and Marenco, 2019     The large increase in total biomass and the substantial improvement in WUEP [water use efficiency] under eCO2 [elevated CO2, 700 ppm], and the sharp decline in leaf area under water stress widen our knowledge on the physiology of this important species for the forest management of large areas in the Amazon region.
Gulyás et al., 2019     Due to climate change, it is important to know to what extent forests will be impacted by atmospheric changes. This study focuses on the height growth response of sessile oak … The relative top heights of the young stands were significantly higher than of the older stands, which means that the overall growing conditions were better in the last 30-35 years due to atmospheric changes than the mean conditions during the lifetime of old stands.

Fire Frequency Declining Since 20th Century Began

Abrams and Nowacki, 2019     Modern assemblages comprise tree genera that are increasingly cool-adapted, shade-tolerant, drought-intolerant pyrophobes. Paleocharcoal data from 1 to 1750 AD indicate a slight increase in burning in southern forests and stable levels in the north, despite the increasing cold associated with the Little Ice Age. … After 1750 AD, charcoal levels in the southern zone form a parabola, increasing rapidly, cresting around 1900, then declining thereafter. … A decline in recent centuries is also evident in the south and the eastern USA as a whole. … The most noticeable feature of the 2000-year fire history here is a large increase in burning during the past ~300 years associated with European land clearance for agriculture. Biomass burning peaked between 1800 and 1900 AD based on historical records, followed by substantial declines after ca. 1940. … The charcoal index between 1 and 1750 AD in this study suggests stable levels of burning in the north and a slight increase in the south. It is interesting to note that southern forests exhibited a slight increase in burning associated with the Medieval Warm Period (ca. 950 to 1250 AD) but did not decline with the LIA (ca. 1350–1850; Mann et al. 2009). In northern forests, the charcoal index dipped between 1000 and 1200 AD and then increased at the start of the LIA, the opposite of what would be expected from climate control. … The large decrease in fire after 1940, mainly attributed to active fire suppression via the Smokey Bear campaign (Abrams 2010), occurred during a significant warming period and may represent another important fire-climate disconnect. However, the decline of burning may have been facilitated by lessening frequency and intensity of drought after 1930 (Fig. 1; McEwan et al. 2011).

Global Warming Reduces Mortality. Cold Kills.

Cheng et al., 2018     We collected daily time-series data on all-cause deaths and weather variables for the five most populous Australian cities (Sydney, Melbourne, Brisbane, Adelaide, and Perth), from 2000 to 2009. … The greatest percentage increase in mortality was for cold (2.0%, 95% confidence interval (CI): 1.4%, 2.6%), followed by heat (1.2%, 95% CI: 0.7%, 1.7%), and temperature variability (0.5%, 95% CI: 0.3%, 0.7%). There was no clear temporal pattern in mortality risk associated with any temperature exposure in Australia. Heat, cold and temperature variability together resulted in 42,414 deaths during the study period, accounting for about 6.0% of all deaths. Most of attributable deaths were due to cold (61.4%), and noticeably, contribution from temperature variability (28.0%) was greater than that from heat (10.6%).

Deng et al., 2019     Using daily mortality and meteorological data from 2009 to 2016 … [w]e analysed 89 467 non-accidental deaths; 4131 were attributable to overall temperatures, with an attributable fraction of 4.75% (95% eCI 2.33% to 6.79%). Most of the mortality burden was caused by cold (4.08%; 0.86% to 7.12%), whereas the burden due to heat was low and non-significant (0.67%; −2.44% to 3.64%). Extreme cold (1.17%; 0.58% to 1.69%) was responsible for 24.6% (ie, 1.17% divided by 4.75%) of the total death burden. In the stratification analyses, attributable risk due to cold was higher for cardiovascular than respiratory disease (6.18% vs 3.50%). … Previous studies have found that most of the mortality burden is caused by exposure to cold days, with comparatively lower attributable risk, or even none, due to heat exposure. For example, Hajat et. al showed that all-cause mortality attributable to heat ranged from 0.37% in London (1976–2003) to 1.45% in Milan (1985–2002), and another study conducted in London from 1986 to 1996 found that attributable fraction of mortality for each 1°C decrease below a threshold of 15°C was 5.42% (4.13% to 6.69%), with no burden due to heat.

Díaz et al., 2019     Results: The results show that the RRs [relative risks/mortality due to cold weather] for Spain as a whole were 1.12 (95% CI: 1.08 1.16) for the first period [1983-1992], 1.15 (95% CI: 1.09 1.22) for the second [1993-2003] and 1.18 (95% CI: 1.10 1.26) for the third [2004-2013]. The impact of cold days has risen slightly over time, though the differences were not statistically significant. These findings show a clearly different behaviour pattern to that previously found for heat. Conclusion: The results obtained in this study do not show a downward trend for colds days [during 1983-2013]. … In the first place, here in Spain daily cold-related mortality is higher than heat-related mortality (3.5 deaths/day versus 3.0 deaths/day) (Carmona et al., 2016a). … In the case of Spain, studies conducted for the city of Madrid by age group showed heat-related mortality to be decreasing across all age groups, while cold-related mortality was increasing, particularly in the over-65 age bracket (Díaz et al., 2015b). … One study recently undertaken in the city of Madrid shows that heat-related mortality in Madrid across the period 2001–2009 accounted for 344 deaths, whereas cold-related mortality accounted for a total of 1473 deaths, i.e., fourfold that of heat.

Lin et al., 2019     Temperature-related risks varied with study area and health outcome. Meta-analysis showed greater all-cause mortality risk occurred in low temperatures than in high temperatures. Integrated RR [relative risk] of all-cause mortality was 1.71 (95% confidence interval [CI]:1.43–2.04) in the 5th percentile [cold] temperature and 1.10 (95% CI: 1.05–1.15) in the 95th percentile [hot] temperature, while the lowest mortality risk was in the 60th percentile temperature (22.2 °C).

No Increasing Trends In Intense Storms, Hurricanes

Gertler and O’Gorman     The circulation of the Northern Hemisphere extratropical troposphere has changed over recent decades [1979-2017], with marked decreases in extratropical cyclone activity and eddy kinetic energy (EKE) in summer and increases in the fraction of precipitation that is convective in all seasons. Decreasing EKE in summer is partly explained by a weakening meridional temperature gradient, but changes in vertical temperature gradients and increasing moisture also affect the mean available potential energy (MAPE), which is the energetic reservoir from which extratropical cyclones draw. … These results connect changes in the atmospheric mean state with changes in both large-scale and convective circulations, and they suggest that extratropical cyclones can weaken even as their associated convection becomes more energetic.

Trenary et al., 2019     The impact of anthropogenic forcings on tropical North Atlantic hurricane potential intensity (PI) is evaluated in CMIP5 models for the period 1958‐2005. Eleven models are examined, but only seven models have a forced response that is distinguishable from internal variability. The use of discriminant analysis to optimize detectability does not yield a clear, common climate change signal. Of the seven models with a significant response, one has a negative linear trend while two have a positive linear trend. The trend in PI [hurricane potential intensity] is not even consistent among reanalyses, although this difference is not statistically significant because of large uncertainties. Furthermore, estimates of PI internal variability have significantly different variances among different reanalysis products. These disagreements between models, reanalysis products, and between models and reanalyses, in conjunction with relatively large uncertainties, highlight the difficulty of detecting and attributing observed changes in North Atlantic hurricane potential intensity.

No Increasing Trend In Drought/Flood Frequency, Severity

Mishra et al., 2019     Millions of people died due to famines in India in the nineteenth and twentieth centuries; however, the relationship of historical famines with drought is complicated and not well understood. Using station‐based observations and simulations, we reconstruct soil moisture (agricultural) drought in India for the period 1870–2016. We show that over this century and a half period, India experienced seven major drought periods (1876–1882, 1895–1900, 1908–1924, 1937–1945, 1982–1990, 1997–2004, and 2011–2015) based on severity‐area‐duration analysis of reconstructed soil moisture. Out of six major famines (1873–74, 1876, 1877, 1896–97, 1899, and 1943) that occurred during 1870–2016, five are linked to soil moisture drought, and one (1943) was not. The three most deadly droughts (1877, 1896, and 1899) were linked with the positive phase of El Niño–Southern Oscillation. Five major droughts were not linked with famine, and three of those five nonfamine droughts occurred after Indian independence in 1947.

Toomey et al., 2019     Increased cold event frequency over the continental United States is often indicative of negative phases of the NAO (Thompson & Wallace, 2001), and both records above bear similarities to the 1,000‐year long NAO reconstruction of Trouet et al. (2009; Figure 4b). While the winter moisture budget (evaporation minus precipitation) over much of Eastern North America changes little between NAO phases (Hurrell, 1995), persistent weakness of the western end of the subtropical ridge—implied by more negative NAO conditions—is consistent with enhanced hurricane tracking toward the East Coast (e.g., Kossin et al., 2010). Increased hurricane rainfall may therefore explain, in part, intervals of increased flood frequency on the Susquehanna during the late Holocene as well as nearby rivers such as the Little Tennessee River, North Carolina‐Tennessee (L. Wang & Leigh, 2012), and Greenbrier River, West Virginia (Aldred, 2010). Negative NAO conditions may also foster stronger tropical cyclone genesis, overall, in the Main Development Region (~10–20° N, 20–85° W; Figure 4a). … We find more frequent deposition from large floods when Chesapeake Bay SSTs, based on Mg/Ca ostracodes measurements (Figure 4c), were colder than normal (Cronin et al., 2003, 2010).

Natural CO2 Emissions A Net Source, Not A Net Sink

Dixit et al., 2019     The key role of oceans in the global climatic system can be accurately quantified by the measurement of CO 2 exchange across air–sea interface. The direction and magnitude of this CO 2 exchange are mainly governed by the gradient of partial pressure of carbon dioxide (pCO 2 ) at the air–sea interface. … Derived fluxes showed that BOB [Bay of Bengal] is a net annual source (0.440 g-C/m 2 /year for year 2014) of CO 2 at mooring location with significant seasonality effects.
Tian et al., 2019    The equatorial Pacific is the major source region for outgassing CO2 to the atmosphere, annually amounting to 0.44±0.14 PgC (Feely et al. 1999; Ishii et al. 2014).
Terlouw et al., 2019A statistical evaluation of nearly ten years of high-resolution surface seawater carbon dioxide partial pressure (pCO2) time-series data collected from coastal moorings around O’ahu, Hawai’i suggest that these coral reef ecosystems were largely a net source of CO2 to the atmosphere between 2008 and 2016. … The observed inter-annual increase in pCO2sw at CRIMP-2 over the study period may reflect the influence of climate oscillations on local conditions: Firstly, increased seawater temperature both directly increases pCO2sw and may enhance rates of respiration, which also increase pCO2sw. Secondly, reduced trade wind speed increases the water residence time on the reef, allowing for more build-up of CO2 in seawater.

Lønborg et al., 2019     The Great Barrier Reef: A source of CO2 to the atmosphere … Seasonal variations in air-sea CO2 fluxes on the Great Barrier Reef reveal a strong CO2 release during the early-dry season. The Great Barrier Reef is overall a net source of CO2. CO2 fluxes are largely controlled by cross-shelf advection of oversaturated warm surface waters from the Coral Sea.

CO2 Changes Lag Warming

Muschitiello et al., 2019     Deep-water circulation changes lead North Atlantic climate during deglaciation … The analysis reveals that changes in Nordic Seas NADW [North Atlantic Deep Water] formation occurred before the climate shifts into and out of GS-1 (YD) [Younger Dryas deglaciation/warming, ~11,700 yrs before present] by 385 ± 32 (1σ bounds) and 447 ± 27 years, respectively, and that weakening of Nordic Seas NADW [North Atlantic Deep Water] occurred 437 ± 79 years prior to the first signs of pCO2 rise near the start of GS-1 (YD) [Younger Dryas deglaciation/warming, ~11,700 yrs before present] . Importantly, the latter finding substantiates the hypothesised lag between AMOC reduction and pCO2 rise during early deglaciation and is observed in climate simulations as a transient response of the global efficiency of the biological pump to AMOC slowdown.

Miscellaneous

Peak Oil as a “wrong and misleading” concept

Bardi, 2019     Today, 20 years have passed since the publication of the ground-breaking Scientific American report [1]. The expected world peak has not arrived, at least in terms of a reduction of the global supply of liquid fuels [11] and, in general, the concept of peak oil has faded from the mainstream discussion as well as from the scientific literature. ASPO international seems to have disappeared as an active association around 2012–2013, although some national branches of the association still exist. The generally accepted explanation for the fading interest in the concept attributes it to the “wrong predictions” of the date of the peak and, from there, most mainstream reports tend to define the whole concept  as wrong and misleading.

CO2 concentrations naturally higher (756 ppm) in winter (caves)?

Al-Manmi et al., 2019     Calcite growth at site 1 reflects a seasonal growth pattern in which higher cave air CO2 concentrations inhibit CO2 degassing from cave dripwater and thus inhibit calcite precipitation. This process is driven by varying temperature gradient between surface air and cave air, which drives the ventilation of caves (Banner et al., 2007). The average cave air pCO2 is 596 ppm; in Shalaii Cave air pCO2 rises in mid-January, reaching winter values of 756 ppm and then falling to less than 484 ppm in mid–September, which is nearly atmospheric. The control on cave air pCO2 is complex; in the winter there is a rise in cave air pCO2, which is primarily a result of reversals in chimney ventilation driven by temperature being in contrast between the cave interior and exterior, with additional transient effects caused by synoptic scale atmospheric pressure and wind conditions (Mattey et al., 2008).

Climate sensitity to quadrupled CO2 1.88 K to 2.27 K?

Chen et al., 2019     Climate sensitivity and feedbacks are basic and important metrics to a climate system. They determine how large surface air temperature will increase under CO2 forcing ultimately, which is essential for carbon reduction policies to achieve a specific warming target. In this study, these metrics are analyzed in a climate system model newly developed by the Chinese Academy of Meteorological Sciences (CAMS-CSM) and compared with multi-model results from the Coupled Model Comparison Project phase 5 (CMIP5). Based on two idealized CO2 forcing scenarios, i.e., abruptly quadrupled CO2 and CO2 increasing 1% per year, the equilibrium climate sensitivity (ECS) and transient climate response (TCR) in CAMS-CSM are estimated to be about 2.27 and 1.88 K, respectively. The ECS is near the lower bound of CMIP5 models whereas the TCR is closer to the multi-model ensemble mean (MME) of CMIP5 due to compensation of a relatively low ocean heat uptake (OHU) efficiency. The low ECS is caused by an unusually negative climate feedback in CAMS-CSM, which is attributed to cloud shortwave feedback (λSWCL) over the tropical Indo-Pacific Ocean.
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