Six indicators to measure the climate emergency

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Methodology

To choose the indicators for this article, we drew inspiration from the climate dashboards of the Met Office and the National Oceanic and Atmospheric Administration (NOAA).

We have taken some of the sources listed in these dashboards:

→ National Oceanic and Atmospheric Administration (United States): temperature measurements (Global Temp), CO concentration2 (Mauna Loa site and global mean sea surface measurements) and the heat absorbed by the oceans (Levitus).
→ Met Office (United Kingdom): temperature measurements (HadCRUT 5 model).
→ National Aeronautics and Space Administration (United States): temperature measurements (Gistemp), ocean levels, ice surface at the poles (NSIDC).
→ Berkeley Earth (United States): temperature measurements.
→ National Center for Space Studies (France): ocean level measurements (Aviso).
→ University of Colorado (United States): ocean level measurements.
→ European Organization for the Exploitation of Meteorological Satellites (Europe): measurements of the surface of ice at the poles (Satellite Application Facility on Ocean and Sea Ice).
→ World glacier monitoring service (United Nations): measurements of ice melting.

With the exception of the CO concentration2 of which we provide the raw measurement from NOAA, the other five indicators are presented in the form of a deviation or anomaly compared to a reference period. This varies according to the indicators: 1850-1900 for temperatures, 1981-2010 for sea ice or the heat stored by the oceans… In most cases, this period is determined according to the start date of the observations.

Precisions on temperature data

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For temperatures, we have adopted the methodology of the Intergovernmental Panel on Climate Change (IPCC), which proposes the years 1850-1900 as the reference period, a period during which temperatures are considered stable. For each of the datasets, we have therefore normalized the values ​​to allow a comparison with this period.

According to the IPCC, the temperature difference between 1850-1900 and the period 1981-2010 amounts to +0.69°C. If we do the same calculation with the data we selected, we get a similar difference (+0.689°C).

We have thus chosen to calculate the average of the four data sets available to us in order to obtain a general average trend of the monthly observations. Being subject to seasonal variations, we then smoothed them by calculating an average over the last hundred and twenty months.

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