Monitoring Global Warming

Abstract

Because the rise in global average surface temperature ceased early in the last decade, there is good reason to monitor developments closely. The key question is whether the upward trend resumes. The various official bodies are unanimous in asserting that it will, explaining the current departure from the long-term trend as a natural variation. Short-term variations (generally 2–3 years) are to a considerable extent explained by the El Niño-Southern Oscillation (ENSO) and volcanic eruptions. But departures from the trend lasting 3 years or more have yet to be adequately explained. It is therefore not possible to say whether the current departure is typical of previous departures, or whether it marks the beginning of a change in the long-term trend. A simple method of monitoring is proposed. It is based on graphs showing the short-term and medium-term trends in the data of each of the main providers. As the data are published monthly, a close check can be kept on developments.