The post below updates the UAH (U. of Alabama in Huntsville) record of air temperatures over land and ocean. But as an overview consider how recent rapid cooling completely overcame the warming from the last 3 El Ninos (1998, 2010 and 2016). The UAH record shows that the effects of the last one were gone as of March 2021. (UAH baseline is now 1991-2020). Now in September, cooling has reversed in both NH land and ocean, offset by SH land and ocean warming.For reference I added an overlay of CO2 annual concentrations as measured at Mauna Loa. While temperatures fluctuated up and down ending flat, CO2 went up steadily by ~55 ppm by 2020, a 15% increase.
Furthermore, going back to previous warmings prior to the satellite record shows that the entire rise of 0.8C since 1947 is due to oceanic, not human activity.
The animation is an update of a previous analysis from Dr. Murry Salby. These graphs use Hadcrut4 and include the 2016 El Nino warming event. The exhibit shows since 1947 GMT warmed by 0.8 C, from 13.9 to 14.7, as estimated by Hadcrut4. This resulted from three natural warming events involving ocean cycles. The most recent rise 2013-16 lifted temperatures by 0.2C. Previously the 1997-98 El Nino produced a plateau increase of 0.4C. Before that, a rise from 1977-81 added 0.2C to start the warming since 1947.
Importantly, the theory of human-caused global warming asserts that increasing CO2 in the atmosphere changes the baseline and causes systemic warming in our climate. On the contrary, all of the warming since 1947 was episodic, coming from three brief events associated with oceanic cycles.
September Update Cooler NH Ocean and Land 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. While you will hear a lot about 2020 temperatures matching 2016 as the highest ever, that spin ignores how fast has the cooling set in. The UAH data analyzed below shows that warming from the last El Nino is now fully dissipated with chilly temperatures setting in all regions. The peak NH summer month of July saw some warming most pronounced in the SH, now reversed by cooling in August and September.
UAH has updated their tlt (temperatures in lower troposphere) dataset for September. 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. Last month showed air temps over SH land and ocean moved upward, while NH land and ocean cooled.
Note: UAH has shifted their baseline from 1981-2010 to 1991-2020 beginning with January 2021. In the charts below, the trends and fluctuations remain the same but the anomaly values change with the baseline reference shift. Data for lower troposphere is here .
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. Thus the cooling oceans now portend cooling land air temperatures to follow. 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?
After a technical enhancement to HadSST3 delayed updates Spring 2020, May resumed a pattern of HadSST updates toward the following month end. For comparison we can look at lower troposphere temperatures (TLT) from UAHv6 which are now posted for September. The temperature record is derived from microwave sounding units (MSU) on board satellites like the one pictured above. Recently 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.
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). The graph below shows monthly anomalies for ocean temps since January 2015.In Jan-March 2021 SH dropped sharply, pulling the Global anomaly down with SH matching the coldest in this period. March drops in the Tropics and NH made those regions at their coldest since 01/2015. In June 2021 despite an uptick in NH, the Global anomaly dropped back down due to a record low in SH along with a Tropical cooling. The summer warm pulse in NH was mild this year, with NH peaking in July, pulling up Global anomaly slightly with an assist from the Tropics. Now in September Tropics are flat, NH is down, offset by SH warming.
Land Air Temperatures Tracking Downward in 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 September is below.
Here we have fresh evidence of the greater volatility of the Land temperatures, along with extraordinary departures by SH land. Land temps are dominated by NH with a 2021 spike in February, followed by cooling down to April. Then NH land warmed with a second NH spike peaking in July. Note how cold have been SH land temperatures in 2021, with two lows in Jan. and again in July. Now SH has spiked upward, raising the Global land anomaly despite NH cooling.
The Bigger Picture UAH Global Since 1995
The chart shows monthly anomalies starting 01/1995 to present. The average anomaly is 0.04, since this period is the same as the new baseline, lacking only the first 4 years. 1995 was chosen as an ENSO neutral year. The graph shows the 1998 El Nino after which the mean resumed, and again after the smaller 2010 event. The 2016 El Nino matched 1998 peak and in addition NH after effects lasted longer, followed by the NH warming 2019-20, with temps having returned again to the mean March-June, with an uptick in July-September.
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. Since the ocean has 1000 times the heat capacity as the atmosphere, that cooling is a significant driving force. 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.