Tag Archives: global temperature

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.

Serious Quality Problems with Global Surface Temperature Data

McKitrick, Ross. A Critical Review of Global Surface Temperature Data Products (August 5, 2010).  https://ssrn.com/abstract=1653928 or http://dx.doi.org/10.2139/ssrn.1653928

There are three main global temperature histories: the combined CRU-Hadley record (HADCRU), the NASA-GISS (GISTEMP) record, and the NOAA record. All three global averages depend on the same underlying land data archive, the Global Historical Climatology Network (GHCN). Because of this reliance on GHCN, its quality deficiencies will constrain the quality of all derived products.

The number of weather stations providing data to GHCN plunged in 1990 and again in 2005. The sample size has fallen by over 75% from its peak in the early 1970s, and is now smaller than at any time since 1919. The collapse in sample size has increased the relative fraction of data coming from airports to about 50 percent (up from about 30 percent in the 1970s). It has also reduced the average latitude of source data and removed relatively more high-altitude monitoring sites.

Oceanic data are based on sea surface temperature (SST) rather than marine air temperature (MAT). All three global products rely on SST series derived from the ICOADS archive. ICOADS observations were primarily obtained from ships that voluntarily monitored SST. Prior to the post-war era, coverage of the southern oceans and polar regions was very thin. Coverage has improved partly due to deployment of buoys, as well as use of satellites to support extrapolation. Ship-based readings changed over the 20th century from bucket-and-thermometer to engine-intake methods, leading to a warm bias as the new readings displaced the old. Until recently it was assumed that bucket methods disappeared after 1941, but this is now believed not to be the case, which may necessitate a major revision to the 20th century ocean record. There is evidence that SST trends overstate nearby MAT trends.

The quality of data over land, namely the raw temperature data in GHCN, depends on the validity of adjustments for known problems due to urbanization and land-use change. The adequacy of these adjustments has been tested in three different ways, with two of the three finding evidence that they do not suffice to remove warming biases.

The overall conclusion of this report is that there are serious quality problems in the surface temperature data sets that call into question whether the global temperature history, especially over land, can be considered both continuous and precise. Users should be aware of these limitations, especially in policy-sensitive applications.

Global Temperature Update May 2017

Source: DrRoySpencer

Southern Hemisphere Climate Data Made Up to Fill Gaps

According to overseers of the long-term instrumental temperature data, the Southern Hemisphere record is “mostly made up”.  This is due to an extremely limited number of available measurements both historically and even presently from the south pole to the equatorial regions. click here for the notrickszone

Ocean Heating and Cooling Affects Global Temperatures

A. Oka and M. Watanabe. The post-2002 global surface warming slowdown caused by the subtropical Southern Ocean heating acceleration. Geophysical Research Letters, DOI: 10.1002/2016GL072184

The warming rate of global mean surface temperature slowed down during 1998–2012. Previous studies pointed out role of increasing ocean heat uptake during this global warming slowdown, but its mechanism remains under discussion. Our numerical simulations, in which wind stress anomaly in the equatorial Pacific is imposed from reanalysis data, suggest that subsurface warming in the equatorial Pacific took place during initial phase of the global warming slowdown (1998–2002), as previously reported. It is newly clarified that the Ekman transport from tropics to subtropics is enhanced during the later phase of the slowdown (after 2002) and enhanced subtropical Ekman downwelling causes accelerated heat storage below depth of 700 m in the subtropical Southern Ocean, leading to the post-2002 global warming slowdown. Observational data of ocean temperature also support this scenario. This study provides clear evidence that deeper parts of the Southern Ocean play a critical role in the post-2002 warming slowdown.

US Temperature Data Tampering Evidence

“NOAA publishes two US temperature data sets – raw and final. In the graph below, the raw (measured) temperature data is shown in blue, the reported (final) data is shown in red, and satellite temperatures of the troposphere over the United States since 1979 are shown in green.” click here