Moderate May for Land and Ocean Air Temps


With apologies to Paul Revere, this post is on the lookout for cooler weather with an eye on both the Land and the Sea.  UAH has updated their tlt (temperatures in lower troposphere) dataset for May 2020.  Previously I have done posts on their reading of ocean air temps as a prelude to updated records from HADSST3. This month also has a separate graph of land air temps because the comparisons and contrasts are interesting as we contemplate possible cooling in coming months and years.

Presently sea surface temperatures (SST) are the best available indicator of heat content gained or lost from earth’s climate system.  Enthalpy is the thermodynamic term for total heat content in a system, and humidity differences in air parcels affect enthalpy.  Measuring water temperature directly avoids distorted impressions from air measurements.  In addition, ocean covers 71% of the planet surface and thus dominates surface temperature estimates.  Eventually we will likely have reliable means of recording water temperatures at depth.

Recently, Dr. Ole Humlum reported from his research that air temperatures lag 2-3 months behind changes in SST.  He also observed that changes in CO2 atmospheric concentrations lag behind SST by 11-12 months.  This latter point is addressed in a previous post Who to Blame for Rising CO2?

HadSST3 results were delayed with February and March updates only appearing together end of April.  For comparison we can look at lower troposphere temperatures (TLT) from UAHv6 which are now posted for May. The temperature record is derived from microwave sounding units (MSU) on board satellites like the one pictured above.

The UAH dataset includes temperature results for air above the oceans, and thus should be most comparable to the SSTs. There is the additional feature that ocean air temps avoid Urban Heat Islands (UHI). In 2015 there was a change in UAH processing of satellite drift corrections, including dropping one platform which can no longer be corrected. The graphs below are taken from the new and current dataset, Version 6.0.

To enlarge, open image in new tab.

The graph above shows monthly anomalies for ocean temps since January 2015. After all regions peaked with the El Nino in early 2016, the ocean air temps dropped back down with all regions showing the same low anomaly August 2018.  Then a warming phase ensued which peaked in February 2020. As was the case in 2015-16, the warming was driven by the Tropics and NH, with SH lagging behind. After the up and down fluxes, oceans temps in May were similar to last June.

Land Air Temperatures Showing a Seesaw Pattern

We sometimes overlook that in climate temperature records, while the oceans are measured directly with SSTs, land temps are measured only indirectly.  The land temperature records at surface stations sample air temps at 2 meters above ground.  UAH gives tlt anomalies for air over land separately from ocean air temps.  The graph updated for May 2020 is below.

Here we have fresh evidence of the greater volatility of the Land temperatures, along with extraordinary departures, first by NH land with SH often offsetting.   The overall pattern is similar to the ocean air temps, but obviously driven by NH with its greater amount of land surface. The Tropics synchronized with NH for the 2016 event, but otherwise follow a contrary rhythm.  SH seems to vary wildly, especially in recent months.  Note the extremely high anomaly last November, cold in March 2020, and then again a spike in April. In May 2020, all land regions converged, erasing the earlier spikes in NH and SH, and showing anomalies comparable to previous Mays since 2017.

The longer term picture from UAH is a return to the mean for the period starting with 1995.  2019 average rose but currently lacks any El Nino to sustain it.

These charts demonstrate that underneath the averages, warming and cooling is diverse and constantly changing, contrary to the notion of a global climate that can be fixed at some favorable temperature.

TLTs include mixing above the oceans and probably some influence from nearby more volatile land temps.  Clearly NH and Global land temps have been dropping in a seesaw pattern, more than 1C lower than the 2016 peak, prior to these last several months. TLT measures started the recent cooling later than SSTs from HadSST3, but are now showing the same pattern.  It seems obvious that despite the three El Ninos, their warming has not persisted, and without them it would probably have cooled since 1995.  Of course, the future has not yet been written.


  1. Hifast · June 5, 2020

    Reblogged this on Climate Collections.


  2. ren · June 12, 2020

    Meridional circulation during low solar activity gives similar average temperature values as El Nino. This is very confusing because the temperature anomalies are very different in different areas. This is due to the slowing down of the jet stream from west to east. An increase in solar activity will accelerate the jet stream and create La Nina. Peruvian current is very cold, but there is no strong wind along the equator.


    • Ron Clutz · June 12, 2020

      ren, .you are asserting:
      quiet sun->slower jet stream->El Nino, conversely
      active sun->faster jet stream->La Nina.
      Where can I read about those relationships and the evidence for them?


    • Ron Clutz · June 12, 2020

      Maybe you are referring to this:

      Lockwood says that the pattern is related to the effect of ultraviolet light on Earth’s stratosphere, located about 20–50 kilometres above the surface. Ultraviolet light from the Sun is absorbed by ozone in the stratosphere, protecting the planet’s surface but heating the stratosphere in the process. The effect is largest in the tropics, where sunlight is strongest, and the temperature gradients set up a global pattern of upper-atmosphere winds, including the Northern and Southern Hemisphere jet streams.

      “Relatively simple models have demonstrated that heating the equatorial stratosphere can push the jet streams apart just a little bit,” says Lockwood. Similarly, cooling the stratosphere — as occurs during periods of low solar activity — allows the jet streams to shift towards the Equator. This, he says, seems to have a profound effect on European weather by causing the northern jet stream to block warm maritime air from reaching the continent from the Atlantic Ocean. This, in turn, opens the door to cold, northeasterly winds from Russia and the Arctic.

      It is a pattern seen in weather records from as far back as 1650–1700, an era known as the Maunder minimum, when the Sun was virtually sunspot-free and ‘frost fairs’ were held on the River Thames in London. “Early instrumental records show that those cold winters were accompanied by cold winds from the east,” says Lockwood. Similar wind patterns can be deduced from looking at records of wine harvests in Europe, he adds.

      Not that these correlations are perfect. “The winter of 1684 was the coldest in the whole record,” says Lockwood. “But the very next year, when solar activity was still low, was the third warmest.”
      Ebbing sunspot activity makes Europe freeze


      • ren · June 12, 2020

        This is not an explanation. The explanation is in the lower stratosphere above the polar circle. During low solar activity, the temperature rises in the lower stratosphere. The jet stream in tropopause depends on the excess ozone. This surplus is not evenly distributed. It arises in specific regions and creates a wave.


  3. Ron Clutz · June 12, 2020

    There appears to be a contradiction. If the lower stratosphere warms by more UV absorbed by ozone, then more solar irradience would warm the stratosphere, while less solar would induce cooling, the opposite of what you say. I take your point that the effects differ in different places.


    • ren · June 13, 2020

      You do not take into account the strong ionizing radiation GCR, which during low solar activity works most strongly in the lower stratosphere above the polar circle. The rise in temperature in the lower stratosphere above the polar circle is responsible for the jet stream waving.
      GCR radiation in the lower stratosphere works similarly to UV in the upper. Ozone above the polar circle falls into the lower atmosphere creating waves.


      • ren · June 13, 2020

        In areas where ozone falls from the stratosphere, the surface temperature decreases because the wave that ozone forms displaces water vapor from the upper troposphere.


      • Ron Clutz · June 13, 2020

        Thanks for explaining that. So the same cosmic rays that can increase cloud cover in the troposphere have the effect of making the polar jet stream wavy by making warm spots in the lower stratosphere.


      • Ron Clutz · June 13, 2020

        The situation seems further complicated by seasonal fluctuations like the Arctic oscillation tracked by Judah Cohen.


      • ren · June 13, 2020

        Some scientists have observed the 60-year cycle of force the northern polar vortex.
        “The area of the polar vortex formation is an area of most significant correlations between troposphere pressure and GCR variations independently on the time period and the epoch of the large- scale circulation This suggests a possible contribution of processes taking place in the polar vortex to GCR effects on the lower atmosphere circulation
        ~ 60-year cycle in the climate of the Arctic and the polar vortex state ~60-year cycle in the Arctic climate manifests itself as the rotation of cold and warm epochs which is closely related to the polar vortex states: Strong vortex  warm epoch Strong vortex  warm epoch Weak vortex  cold epoch Weak vortex  cold epoch The transitions between warm and cold epochs in the Arctic detected on the base of sea-level temperatures were found in the early 1920s, 1950s and 1980s Gudkovich et al., Problems of Arctic and Antarctic, 2009 Anomalies of mean yearly sea-level temperatures at latitudes 70-85  N in the Arctic. The reversals of the sign of SA/GCR effects coincide well with the transitions between cold and warm epochs in the Arctic corresponding to the different states of the vortex.”


      • ren · June 13, 2020

        Time evolution of SA/GCR effects on troposphere pressure and the strength of the polar vortex according to NCEP/NCAR reanalysis data 1950-1980 – the period of a weak vortex.

        When the temperature in the lower stratosphere rises above the polar circle, the pressure gradient between the medium and high latitudes in the northern hemisphere drops at 500 hPa in the troposphere.


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