May Temperatures (preliminary)
Global composite temp.: +0.32 C (+0.58 °F) above seasonal average
Northern Hemisphere.: +0.29 C (+0.52 °F) above seasonal average
Southern Hemisphere.: +0.35 C (+0.63°F) above seasonal average
Tropics.: +0.39 C (+0.70 °F) above seasonal average
April Temperatures (final)
Global composite temp.: +0.44 C (+0.79 °F) above seasonal average
Northern Hemisphere.: +0.38 C (+0.68 °F) above seasonal average
Southern Hemisphere.: +0.51 C (+0.92°F) above seasonal average
Tropics.: +0.54 C (+0.97 °F) above seasonal average
Notes on data released June 1, 2019 (v6.0)
May’s globally-averaged, bulk-layer atmospheric temperature anomaly of +0.32°C (+0.58°F) dropped a bit from April’s value and reflected a decline in each of the large-scale areas on which we report. Most interesting is the tropical cooling, down 0.15°C from April, as this may be an indication that the current, modest El Niño is losing its punch. The map of temperature anomalies indicates a decline throughout the tropics.
The conterminous U.S. experienced the coolest May since 1995, though several of the years in between were within 0.1°C of this year’s -0.61°C (-1.10 °F) departure from average and so are statistically tied with 2019. The map indicates the very cool area in the western half of the country that contributed to the strong temperature gradient in the nation’s mid-section. This gradient is where severe weather often forms which was the case this year.
Other cool areas were found in the north Pacific, NW Atlantic, southern Europe and central Russia. It was much warmer than average over far western Canada, Greenland, eastern north Atlantic, western and far eastern Russia. Most of the continental areas in the Southern Hemisphere were modestly warmer than average except Antarctica.
Attesting to the unusually cool western U.S., the Earth’s coldest seasonally-adjusted temperature departure from average occurred near the Grand Canyon in NW Arizona: - 3.3°C (-5.9°F). The warmest spot was over northern Greenland at +4.2°C (+7.6°F).
Spoiler Alert first published March 2019: As noted over the past several months in this report, the drifting of satellites NOAA-18 and NOAA-19, whose temperature errors were somewhat compensating each other, will be addressed in this updated version of data released from March 2019 onward. As we normally do in these situations we have decided to terminate ingestion of NOAA-18 observations as of 1 Jan 2017 because the corrections for its significant drift were no longer applicable. We have also applied the drift corrections for NOAA-19 now that it has started to drift far enough from its previous rather stable orbit. These actions will eliminate extra warming from NOAA-18 and extra cooling from NOAA-19. The net effect is to introduce slight changes from 2009 forward (when NOAA-19 began) with the largest impact on annual, global anomalies in 2017 of 0.02 °C. The 2018 global anomaly changed by only 0.003°C, from +0.228°C to +0.225°C. These changes reduce the global trend by -0.0007 °C/decade (i.e. 7 ten-thousandths of a degree) and therefore does not affect the conclusions one might draw from the dataset. The v6.0 methodology is unchanged as we normally stop ingesting satellites as they age and apply the v6.0 diurnal corrections as they drift.
To-Do List:
There has been a delay in our ability to utilize and merge the new generation of microwave sensors (ATMS) on the NPP and JPSS satellites. As of now, the calibration equations applied by the agency have changed at least twice, so that the data stream contains inhomogeneities which obviously impact the type of measurements we seek. We are hoping this is resolved soon with a dataset that is built with a single, consistent set of calibration equations. In addition, the current non-drifting satellite operated by the Europeans, MetOP-B, has not yet been adjusted or “neutralized” for its seasonal peculiarities related to its unique equatorial crossing time (0930). While these MetOP-B peculiarities do not affect the long-term global trend, they do introduce error within a particular year in specific locations over land.
As part of an ongoing joint project between UAH, NOAA and NASA, Christy and Dr. Roy Spencer, an ESSC principal scientist, use data gathered by advanced microwave sounding units on NOAA, NASA and European satellites to produce temperature readings for almost all regions of the Earth. This includes remote desert, ocean and rain forest areas where reliable climate data are not otherwise available. Research Associate Rob Junod assists in the preparation of these reports.
The satellite-based instruments measure the temperature of the atmosphere from the surface up to an altitude of about eight kilometers above sea level. Once the monthly temperature data are collected and processed, they are placed in a "public" computer file for immediate access by atmospheric scientists in the U.S. and abroad.
The complete version 6 lower troposphere dataset is available here: http://www.nsstc.uah.edu/data/msu/v6.0/tlt/uahncdc_lt_6.0.txt
Archived color maps of local temperature anomalies are available on-line at: http://nsstc.uah.edu/climate/
Neither Christy nor Spencer receives any research support or funding from oil, coal or industrial companies or organizations, or from any private or special interest groups. All of their climate research funding comes from federal and state grants or contracts.
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