Tag Archives: global temperature

20th Century Temperatures Not Unprecedented, China

Quansheng Ge, Haolong Liu, Xiang Ma, Jingyun Zheng, Zhixin Hao. Characteristics of temperature change in China over the last 2000 years and spatial patterns of dryness/wetness during cold and warm periods. Advances in Atmospheric Sciences. August 2017, Volume 34, Issue 8, pp 941–951

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3°C and 0.7°C, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56° ± 0.42°C (100 yr)−1; however, temperatures recorded in the 20th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD 1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20th century warming can primarily be attributed to a mega El Ni˜no–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.

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Global Lower Atmosphere Satellite-Based Temperatures, July 2017

Ocean Cycles Govern Global Temperature Development

“The 60-year ocean cycles govern global temperature development. Yet climate models are still unable to reproduce the empirically well established relationship. Naturally this is all very embarrassing and has since become the object studies on cause-research.” click here

Global Average Surface Temperature Estimates are Unreliable

“The peer-reviewed study by two scientists and a veteran statistician looked at the global average temperature datasets (GAST) which are used by climate alarmists to argue that recent years have been “the hottest evah” and that the warming of the last 120 years has been dramatic and unprecedented.” click here for news article.

The abstract of the study is below. The study itself is here.

“The objective of this research was to test the hypothesis that Global Average Surface Temperature (GAST) data, produced by NOAA, NASA, and HADLEY, are sufficiently credible estimates of global average temperatures such that they can be relied upon for climate modeling and policy analysis purposes. The relevance of this research is that the validity of all three of the so- called Lines of Evidence in EPA’s GHG/CO2 Endangerment Finding require GAST data to be a valid representation of reality. In this research report, the most important surface data adjustment issues are identified and past changes in the previously reported historical data are quantified. It was found that each new version of GAST has nearly always exhibited a steeper warming linear trend over its entire history. And, it was nearly always accomplished by systematically removing the previously existing cyclical temperature pattern. This was true for all three entities providing GAST data measurement, NOAA, NASA and Hadley CRU. As a result, this research sought to validate the current estimates of GAST using the best available relevant data. This included the best documented and understood data sets from the U.S. and elsewhere as well as global data from satellites that provide far more extensive global coverage and are not contaminated by bad siting and urbanization impacts. Satellite data integrity also benefits from having cross checks with Balloon data. The conclusive findings of this research are that the three GAST data sets are not a valid representation of reality. In fact, the magnitude of their historical data adjustments, that removed their cyclical temperature patterns, are totally inconsistent with published and credible U.S. and other temperature data. Thus, it is impossible to conclude from the three published GAST data sets that recent years have been the warmest ever –despite current claims of record setting warming. Finally, since GAST data set validity is a necessary condition for EPA’s GHG/CO2 Endangerment Finding, it too is invalidated by these research findings.”

Surface-Warming Hiatus Attributable to Internal Variability

Christopher Hedemann, Thorsten Mauritsen, Johann Jungclaus1 and Jochem Marotzke. The subtle origins of surface-warming hiatuses. Nature Climate Change, 7:336-339 (2017). doi:10.1038/nclimate3274 

During the first decade of the twenty-first century, the Earth’s surface warmed more slowly than climate models simulated1 . This surface-warming hiatus is attributed by some studies to model errors in external forcing2–4 , while others point to heat rearrangements in the ocean5–10 caused by internal variability, the timing of which cannot be predicted by the models1 . However, observational analyses disagree about which ocean region is responsible11–16. Here we show that the hiatus could also have been caused by internal variability in the top-of-atmosphere energy imbalance. Energy budgeting for the ocean surface layer over a 100-member historical ensemble reveals that hiatuses are caused by energy-flux deviations as small as 0.08 W m−2 , which can originate at the top of the atmosphere, in the ocean, or both. Budgeting with existing observations cannot constrain the origin of the recent hiatus, because the uncertainty in observations dwarfs the small flux deviations that could cause a hiatus. The sensitivity of these flux deviations to the observational dataset and to energy budget choices helps explain why previous studies conflict, and suggests that the origin of the recent hiatus may never be identified.

Global Satellite Temperature Products, Methods and Results

Roy W. Spencer, John R. Christy, and William D. Braswell. UAH Version 6 Global Satellite Temperature Products: Methodology and Results. Asia-Pac. J. Atmos. Sci., 53(1), 121-130, 2017  DOI:10.1007/s13143-017-0010-y

Version 6 of the UAH MSU/AMSU global satellite temperature dataset represents an extensive revision of the procedures employed in previous versions of the UAH datasets. The two most significant results from an end-user perspective are (1) a decrease in the global-average lower tropospheric temperature (LT) trend from +0.14o C decade−1 to +0.11o C decade−1 (Jan. 1979 through Dec. 2015); and (2) the geographic distribution of the LT trends, including higher spatial resolution, owing to a new method for computing LT. We describe the major changes in processing strategy, including a new method for monthly gridpoint averaging which uses all of the footprint data yet eliminates the need for limb correction; a new multi-channel (rather than multi-angle) method for computing the lower tropospheric (LT) temperature product which requires an additional tropopause (TP) channel to be used; and a new empirical method for diurnal drift correction. We show results for LT, the midtroposphere (MT, from MSU2/AMSU5), and lower stratosphere (LS, from MSU4/AMSU9). A 0.03o C decade−1 reduction in the global LT trend from the Version 5.6 product is partly due to lesser sensitivity of the new LT to land surface skin temperature (est. 0.01o C decade−1 ), with the remainder of the reduction (0.02o C decade−1 ) due to the new diurnal drift adjustment, the more robust method of LT calculation, and other changes in processing procedures.

 

Global Warming Rates Tied to Ocean Surface Temperature Changes

Shuai-Lei Yao, Jing-Jia Luo, Gang Huang & Pengfei Wang. Distinct global warming rates tied to multiple ocean surface temperature changesNature Climate Change (2017) doi:10.1038/nclimate3304

The globally averaged surface temperature has shown distinct multi-decadal fluctuations since 1900, characterized by two weak slowdowns in the mid-twentieth century and early twenty-first century and two strong accelerations in the early and late twentieth century. While the recent global warming (GW) hiatus has been particularly ascribed to the eastern Pacific cooling, causes of the cooling in the mid-twentieth century and distinct intensity differences between the slowdowns and accelerations remain unclear. Here, our model experiments with multiple ocean sea surface temperature (SST) forcing reveal that, although the Pacific SSTs play essential roles in the GW rates, SST changes in other basins also exert vital influences. The mid-twentieth-century cooling results from the SST cooling in the tropical Pacific and Atlantic, which is partly offset by the Southern Ocean warming. During the recent hiatus, the tropical Pacific-induced strong cooling is largely compensated by warming effects of other oceans. In contrast, during the acceleration periods, ubiquitous SST warming across all the oceans acts jointly to exaggerate the GW. Multi-model simulations with separated radiative forcing suggest diverse causes of the SST changes in multiple oceans during the GW acceleration and slowdown periods. Our results highlight the importance of multiple oceans on the multi-decadal GW rates.