+0.73 levels. C After the truncation of the NOAA-19 satellite tv for pc knowledge set, are you proud of it?
From Dr. Spencer's Global Warming Blog
by Roy W. Spencer, Ph.D.
The global average lower troposphere (LT) temperature anomaly in version 6.1 for October 2024 was +0.73 degrees. C deviation from the 1991-2020 mean, decrease from the September 2024 anomaly of +0.80 degrees. C
The new (version 6.1) global area-averaged temperature trend (January 1979 to October 2024) is now +0.15 °C/decade (+0.21 °C/decade over land, +0.13 °C/decade over oceans).
Previous trends (version 6.0) through September 2024 were +0.16°C/decade (global), +0.21°C/decade (land), and +0.14°C/decade (sea).
Below you will find background information on the changes leading to the new version (v6.1) of the UAH dataset.
Important points
- The older NOAA-19 satellite has now drifted too far in the diurnal cycle for our drift correction method to provide useful adjustments. For this reason, we have decided to restrict NOAA-19 data processing starting in 2021. This leaves Metop-B as the only satellite in the UAH dataset as of this date. This truncation is consistent with those of previous satellites after orbital drift began to affect temperature measurements.
- This change only slightly reduces recent global heat records and brings our calculated global temperatures more in line with RSS and NOAA satellite datasets from the past two to three years.
- Despite the decline in recent temperatures, the trend is only decreasing by 0.01 degrees Celsius per decade from 1979 to 2024, from +0.16 degrees Celsius per decade to +0.15 degrees Celsius per decade. Recent heat development in 2023-2024 remains record-breaking for the satellite era, with every month since October 2023 setting a record for that calendar month.
background
Monitoring global deep atmospheric temperatures using satellite microwave radiometers (systems originally designed for daily global weather monitoring) has always required corrections and adjustments to the calibrated data to enable long-term trend detection. The most important of these corrections/adjustments are:
- Distortions in satellite calibrationThis requires intercalibration between successively launched satellites when operational coverage overlaps. These adjustments are typically tenths of a degree Celsius.
- Deviation of the orbits from their nominal sun-synchronous observation timesThis requires empirical corrections by comparing a drifting satellite with a non-drifting satellite (the UAH method) or using climate models (the remote sensing systems). [RSS] method which I believe is also used in the NOAA dataset). These corrections can be up to 1 degree. C or more for the lower troposphere (LT) temperature product, particularly over land and in summer.
- Fix for instrument body temperature effects on the calibrated temperature (a problem only with the older MSU instruments which produced false heating).
- Orbital altitude decrease adjustment for the multi-view angle version of the lower troposphere (LT) product (no longer required for the UAH dataset as of version 6.0, which uses multiple channels instead of multiple angles from a single channel.)
The second of these adjustments (daily drift) is the subject of the change from UAH v6.0 to v6.1. The following chart shows the equator crossing times (local solar time) for the various satellites that make up the satellite temperature record. The drift of the satellites (except for the non-drifting Aqua and MetOp satellites, which carry fuel to enable orbit maintenance) provides cooling for the afternoon satellites' LT measurements as the afternoon observation transitions from early afternoon to evening . As the morning satellites drift, their LT temperatures warm as their evening observations transition into the late afternoon.
The red vertical lines indicate the dates after which a satellite's data is no longer included in version 6.0 (UAH) processing, with the NOAA-19 cut added for version 6.1. Note that the NOAA-19 satellite has deviated further in local observing time than any of the previous afternoon satellites. The local NOAA-19 observation times were outside of our training data set, which includes the assumption of linear daily temperature drift with time. Therefore, we have decided that it is now necessary to truncate NOAA-19 data starting in 2021, which we are now doing starting with the October 2024 update.
This begins version 6.1 of our data set, a name change intended to reduce confusion and indicate a material change in our processing. As shown in the figure above, 2020, as the final year of inclusion of NOAA-19 data, roughly coincides with the v6.0 cutoff times of the NOAA-18 and NOAA-14 satellites (afternoon).
This type of change in our processing corresponds to the changes we have made in previous years, after a few years of collecting data to clearly establish that there is a problem. The time delay is necessary because we previously established that two operational satellites in different orbits can diverge in their processed temperatures, only to later converge again. As shown below, we now have enough reasons to shorten the NOAA-19 data set starting in 2021.
Why do we even include a satellite if it drifts in local observation time?
There are three reasons why a daily drifting satellite is included in the processing (with incomplete adjustments): (1) Most satellites in the 1979–2024 recording period were drifting, and therefore their inclusion was necessary to produce a complete, intercalibrated satellite record of temperatures; (2) Two operational satellites (typically one drifting much more than the other) provide a more complete sampling over the month for our gridded data set, which is 2.5 degrees. Lat/Lon resolution; (3) Having two (sometimes three) satellites allows monitoring of potential drifts, i.e. the time series of the difference between two satellite measurements should remain relatively stable over time.
Version 6.1 brings UAH data closer to RSS and NOAA in recent years
Several people noted that our temperature anomalies were warmer than those of the RSS or NOAA satellite products. It now appears that this was due to NOAA-19's orbital drift outside the useful range of our drift correction. The following plot (preliminary, provided to me by John Christy) shows that trimming the NOAA-19 dataset now brings the UAH anomalies more in line with the RSS and NOAA products.
As can be seen, this change has significantly reduced recent global average temperatures. For example, without NOAA-19's truncation, the October anomaly would have been +0.94 degrees. C, but with only MetOp-B after 2020 it is now +0.73 degrees. C
The following table lists various regional deviations of version 6.1 LT from the 30-year average (1991-2020) over the last 22 months (record highs are in red):
| YEAR | MO | GLOBE | NHEM. | SHE. | TROPICAL | USA48 | ARCTIC | AUST |
| 2023 | Jan | -0.07 | +0.06 | -0.21 | -0.42 | +0.14 | -0.11 | -0.45 |
| 2023 | February | +0.06 | +0.12 | +0.01 | -0.15 | +0.64 | -0.28 | +0.11 |
| 2023 | Damage | +0.17 | +0.21 | +0.14 | -0.18 | -1.35 | +0.15 | +0.57 |
| 2023 | April | +0.12 | +0.04 | +0.20 | -0.10 | -0.43 | +0.46 | +0.38 |
| 2023 | May | +0.29 | +0.16 | +0.42 | +0.33 | +0.38 | +0.54 | +0.13 |
| 2023 | June | +0.31 | +0.34 | +0.28 | +0.51 | -0.54 | +0.32 | +0.24 |
| 2023 | July | +0.57 | +0.60 | +0.55 | +0.83 | +0.28 | +0.81 | +1.49 |
| 2023 | Aug | +0.61 | +0.77 | +0.44 | +0.77 | +0.69 | +1.49 | +1.29 |
| 2023 | Sept | +0.80 | +0.83 | +0.77 | +0.82 | +0.28 | +1.12 | +1.15 |
| 2023 | Oct | +0.78 | +0.84 | +0.72 | +0.84 | +0.81 | +0.81 | +0.56 |
| 2023 | November | +0.77 | +0.87 | +0.67 | +0.87 | +0.52 | +1.07 | +0.28 |
| 2023 | Dec | +0.74 | +0.91 | +0.57 | +1.00 | +1.23 | +0.31 | +0.64 |
| 2024 | Jan | +0.79 | +1.01 | +0.57 | +1.18 | -0.19 | +0.39 | +1.10 |
| 2024 | February | +0.86 | +0.93 | +0.79 | +1.14 | +1.30 | +0.84 | +1.14 |
| 2024 | Damage | +0.87 | +0.95 | +0.80 | +1.24 | +0.23 | +1.05 | +1.27 |
| 2024 | April | +0.94 | +1.12 | +0.76 | +1.14 | +0.87 | +0.89 | +0.51 |
| 2024 | May | +0.78 | +0.78 | +0.79 | +1.20 | +0.06 | +0.23 | +0.53 |
| 2024 | June | +0.70 | +0.78 | +0.61 | +0.85 | +1.38 | +0.65 | +0.92 |
| 2024 | July | +0.74 | +0.86 | +0.62 | +0.97 | +0.42 | +0.58 | -0.13 |
| 2024 | Aug | +0.75 | +0.81 | +0.69 | +0.73 | +0.38 | +0.90 | +1.73 |
| 2024 | Sept | +0.80 | +1.03 | +0.56 | +0.80 | +1.28 | +1.49 | +0.96 |
| 2024 | Oct | +0.73 | +0.87 | +0.59 | +0.61 | +1.84 | +0.81 | +1.07 |
The full UAH Global Temperature Report as well as the LT-Global Gridpoint anomaly image for October 2024 and a more detailed analysis from John Christy should be available here in the next few days. Due to the changes resulting from the move from version 6.0 to version 6.1 of the dataset, this might take a little longer this time.
The monthly anomalies for different regions for the four deep layers that we monitor from satellites will be available in the next few days (may also be delayed):
Lower troposphere:
http://vortex.nsstc.uah.edu/data/msu/v6.1/tlt/uahncdc_lt_6.1.txt
Middle troposphere:
http://vortex.nsstc.uah.edu/data/msu/v6.1/tmt/uahncdc_mt_6.1.txt
Tropopause:
http://vortex.nsstc.uah.edu/data/msu/v6.1/ttp/uahncdc_tp_6.1.txt
Lower stratosphere:
http://vortex.nsstc.uah.edu/data/msu/v6.1/tls/uahncdc_ls_6.1.txt
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