Mike’s baseline trick? Do not Panic – A New Base For International Temperature May Cool The Future Debate – Watts Up With That?

Statistical Policy – Prof. Mike Hulme on “politically charged” climate changes from 1961-1990 to 1991-2020:

‘In a moment; Today the world climate has “suddenly” become almost 0.5 ° C warmer.

From the climate depot

Hulme: “In January 12021 a new climatological standard of the World Meteorological Organization (WMO) came into force. “Today’s” climate is now officially represented by the weather statistics for the period 1991-2020, replacing those from 1961-1990. The national meteorological authorities in the Member States are instructed to issue new standard norms for observation stations and related climatological products. The climate will change immediately, one could say; Today the world climate has “suddenly” become almost 0.5 ° C warmer. This is roughly equivalent to resetting the world time or adjusting the exact definition of a measuring device. ”

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“What is the significance of the change to a new WMO from 1991-2020 in January 2021? On the one hand, it is a pragmatic step to redefine the current climate for business applications to that of the last 30 years. On the other hand, a third climatic baseline is brought into play. The “pre-industrial” climate of the late 19th century and the “historical” climate of 1961-1990 are already present, the latter being about 0.3 ° C warmer than the former. And now there is the new ‘today’s’ climate from 1991-2020, which in turn is about 0.5 ° C warmer than the ‘historical climate’ from 1961-1990. ”

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“The combination of a climate tolerance of 2 ° C – or even 1.5 ° C – with a pre-industrial baseline results in a completely different climate target than, for example, using a baseline from 1986-2005, the period largely assumed by the IPCC AR5 Working Group I. their analytical baseline. The choice of both baseline and tolerance is politically charged. They have a significant impact on historical liability for emissions (La Rovere et al., 2002), policy-making (Millar et al., 2017) and possible redress (Roberts & Huq, 2015). “

The paper:

https://www.academia.edu/44905791/Climates_Multiple_Three_Baselines_Two_Tolerances_One_Normal?email_work_card=view-paper

Extracts:

Multiple climatic zones: three baselines, two tolerances, one normal

By Mike Hulme

Excerpt: On Friday, January 1st, 2021, a new climatological standard of the World Meteorological Organization (WMO) came into force. “Today’s” climate is now officially represented by the weather statistics for the period 1991-2020, replacing those from 1961-1990. The national meteorological authorities in the Member States are instructed to issue new standard norms for observation stations and related climatological products. The climate will change immediately, one could say; Today the world climate has “suddenly” become almost 0.5 ° C warmer. This is roughly equivalent to resetting the world time or adjusting the exact definition of a measuring device.

What began in the 1970s and 1980s as the pragmatic selection of the late 19th century as an analytical reference period (Nordhaus, 1977) had acquired great political importance in the 21st century. Although the PACC 2015 formally took the pre-industrial climate as a basis, the exact time term “pre-industrial” was not specified – be it for strategic political reasons (Geden, 2018) or simply because of a lack of awareness of the importance of the election. Various “pre-industrial” baselines have been adopted, either as discursive proxies for a general pre-industrial age or used analytically to test the sensitivity of the “pre-industrial” baseline to different definitions (Schurer et al., 2017). Equal diversity affects the designation of “today’s” climate. Although this often corresponds to a WMO 30-year standard, many other terms for “today’s climate” have been adopted in various IPCC assessments – such as “1990” (in IPCC AR1 and AR2) or in the period 1986-2005 (in AR5 )) – and more generally by individual scientists. The 2015 WMO decision stipulates that the 1961-1990 baseline should continue to be used for the purposes of assessing climate change.

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Three basic climates

What is the significance of the change to a new WMO standard for 1991-2020 in January 2021? On the one hand, it is a pragmatic step to redefine the current climate for business applications to that of the last 30 years. On the other hand, a third climatic baseline is brought into play. The “pre-industrial” climate of the late 19th century and the “historical” climate of 1961-1990 are already present, the latter being about 0.3 ° C warmer than the former. And now there is the new “today’s” climate from 1991-2020, which in turn is about 0.5 ° C warmer than the “historical climate” from 1961-1990. In addition to these three climate baselines, there are two climate tolerances anchored in the PACC of 1.5 ° and 2 ° C.

Climate normals and baselines give the rather immaterial concept of climate a precise numerical form: an idea that imposes a certain amount of imagination on the human experience of atmospheric chaos (Hulme, 2016). While baselines can be either descriptive, predictive and / or normative, climate tolerances are more explicitly normative. The acceptance of certain basic lines and tolerances is therefore an openly political process with geopolitical, ethical and technological consequences. As with the introduction of other universal reference markers – for example the Greenwich Meridian as zero longitude, the metric system or the formula for water as H2O – these processes include historical trajectories, cultural imaginaries, strange coincidences and power dynamics. I will examine these eventualities in more detail in a subsequent article.

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“Dangerous climate change” can be defined either absolutely or relatively. If it is defined relatively, however, it is not only important how much deviation from “normal” is considered tolerable, but also what is considered to be “normal” at all. Combining a climate tolerance of 2 ° C – or even 1.5 ° C – with a pre-industrial baseline results in a very different climate goal than, for example, using a baseline from 1986-2005, the period widely adopted by the IPCC AR5 Working Group I. analytical baseline. The choice of both baseline and tolerance is politically charged. They have a significant impact on historical liability for emissions (La Rovere et al., 2002), policy-making (Millar et al., 2017) and possible redress (Roberts & Huq, 2015).

Some thoughts from Anthony:

The only temperature diagram that is not a slave to the baseline selection is the absolute temperature. Anomaly-based temperature is a statistical construct based on the statistician’s assumptions and decisions.

Here is an example of an absolute temperature plot from NASA GISS data.

Absolute temperature graph from NASA GISS data: 1880 to 2016

In order to determine the “absolute temperature” precisely, we would of course draw the Kelvin scale. But few understand the Kelvin scale; Fahrenheit and Celsius scales determine human perception.

Temperature trends indeed Don’t change with changes to the baselinebut each time there is a perceived step up, that is, ‘In an instant; Today the world climate has “suddenly” become almost 0.5 ° C warmer. It could be used for political and propaganda purposes without ever acknowledging that it was a statistical upward trend and not real.

But Hulme has it backwards, we won’t see a step above the normal temperature reports.

As the baseline rises, the anomaly temperatures in the future, ie the deviation from normal, will be lower because the “normal baseline” is now higher.

In an email exchange with Dr. Roy Spencer notes:

No, the climate doesn’t suddenly get warmer. The new baseline is warmer, but since the baseline is warmer, all temperatures will be cooler in proportion. For humans it is not important whether the global average temperature is (for example) 60 degrees. However, they do pay attention to how high the temperatures are above normal, and for at least the next 10 years those numbers will be lower.

Dr. Roy Spencer, via email 1/16/21

So it seems that this won’t be an issue in the future. Lower temperatures above normal will cool some future debate.

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