Globally averaged mole fractions of carbon dioxide (CO 2) have already exceeded 410 parts per million (ppm), and if the CO 2 concentration follows the same pattern as in previous years, it could reach or exceed 414 ppm in 2021. All key climate indicators and impact information provided in this report show relentless, continuing climate change, an increasing occurrence and intensification of high-impact events and severe losses and damages affecting people, societies and economies.Ĭoncentrations of the major greenhouse gases continued to increase in 20. This underscores the robustness of climate science based on the physical laws governing the behaviour of the climate system. While understanding of the climate system and computing power have increased since then, the basic message remains the same, and we now have 28 more years of data that show significant temperature increases over land and sea, as well as other changes, such as sea-level rise, melting of sea ice and glaciers and changes in precipitation patterns. The report was initiated due to the concerns raised at that time about projected climate change. It has been 28 years since the World Meteorological Organization issued the first state of the climate report in 1993. Foreword by Professor Petteri Taalas, Secretary-General of the World Meteorological Organization