Resolves positive if the long-run [20 year] global mean temperature average raises more than 3.0°C vs. the 1850-1900 average before 2050

Resolves negative otherwise

https://web.archive.org/web/20220518083042/https://library.wmo.int/doc_num.php?explnum_id=11178

If the temperature reaches the threshold, then falls back below that level the contract still resolves positive.

The temperature must heat more than the threshold in the title for the contract to resolve positive, to whatever precision measured. So, if a reputable source gives the midpoint temperature increase as 3.01°C, the contrast will resolve positive, but not if the source lists 3.00°C. If the source uses a confidence interval, the contract will resolve based on the reported midpoint.