Copernicus Service catalogue

This application monitors the evolution of the global surface air temperature over recent decades until the present and estimates with a simple model (using a 30-year linear trend),
the level of global warming at the date up to which the trend is calculated and the date when global warming will reach the 1.5°C limit of the Paris agreement if the trend continues at that same rate.

The application presents a graphic showing, up to the selected month, the change in global average surface air temperature monthly means with respect to the pre-industrial period. Superimposed on it,
a line depicts the linear trend of the global temperature increase over the preceding 30-years. A grey box is used to indicate the estimated ‘global warming’ at the time of the selected month and
a red marker indicates the time in the future when the trend line reaches the 1.5°C limit. The estimated 1.5°C limit date, i.e. the intersection between the temperature linear trend and 1.5° limit line,
varies depending on the set of years used for the trend estimation. By using a slider the user can chose the 30-year window for which these numbers are given and see how the estimates change with time.

The application is first and foremost a monitoring tool and the indicative future date is there for illustrative purposes only and should not be interpreted as a forecast.

The application is presented as a simple x-y plot, where the x-axis is time starting in 1979 and the y-axis the temperature variation with respect to the pre-industrial period. The plot shows:

• in solid light and dark grey, the monthly average temperature anomalies, with respect to pre-industrial era, up to the month selected via the provided slider;
• the dark grey line shows values corresponding to the 30 years before the selected month, while the light grey line represents the remaining values back to the first (January 1979) and up to the most recent available month;
• a solid red line, with the linear global temperature trend calculated from the values of the thirty-year period up until the selected month (the period is indicated by dark grey monthly values);
• a red circle and a thin vertical red dashed line mark the point where the trend intersects the horizontal dashed redline that represents a global warming increase of 1.5°C, indicated by the red box;
• a vertical thin grey line placed at the selected month;
• a horizontal dashed grey line and grey box, mark the point and the corresponding global warming estimate where the trend line intersect the vertical thin grey line placed at the selected month;
• Sentences at the top left of the plot, indicate the global warming estimate and the corresponding date of the two intersections of the trend line, as described above;
• an orange shaded area represents the uncertainty associated with both past values of and future climate projections of global warming, as reported in the summary for policymakers of the 2018 IPCC special report “Global Warming of 1.5°C”.
• an orange line indicate the associated IPCC ‘likely’ estimate of the time interval
  during which global warming will reach 1.5°C above pre-industrial

In this application:

• "Global warming" at a point in time refers to the increase in a 30-year average, centred on the specified time, of Earth’s global surface temperature relative to the pre-industrial period;
• "Reaching the limit" refers to the moment when the central time of the 30-year average temperature equals 1.5˚C above pre-industrial values;
• “Pre-industrial values” refers to the approximation of the surface air temperature of this era from the IPCC ‘Global warming of 1.5°C’ report, namely the 1850-1900 average based on instrumental data, an estimated 0.63°C (±0.06°) below the period 1981-2020.

Limitations of the method

The simple model here is not intended as a prediction, rather it is to illustrate the most simple yet
still plausible model for how global warming may evolve in the coming years and decades.
Introducing further datasets and slightly different methods for estimating the trend would slightly
affect the numbers shown, but would not change the fact that the model is a simplification and
that a more complex model is needed to encompass the full uncertainty envelope. The envelope
given by the projections, as well as the ‘likely’ estimate based on those, as indicated by the
orange bar, taken from the IPCC 1.5°C report are indicative of the level of uncertainty associated
with making such a prediction.
The dataset used only starts in 1971 and is adjusted to be relative to pre-industrial by assuming
that the 1981-2010 reference period is 0.63°C warmer than the pre-industrial era, where the
definition of pre-industrial values refers to the IPCC’s approximation of the temperature of the
pre-industrial era, namely the 1850-1900 average based on instrumental data.

User-selectable parameters

• Year and month (slider): the final month of the 30-years-window used to estimate the global temperature anomaly
  linear trend. Ranging from December 2008 to the most recent available month, with monthly frequency for the most recent
  twelve months and yearly frequency over the rest of the period.