Climate change is most commonly measured using the average surface temperature of the planet. Estimates from the UK Met Office, NASA, US National Climatic Data Centre and Berkeley Earth all show a rising trend in average global temperature over the last century. The temperature in the last decade was roughly 0.9°C above 1900 levels.
Year-on-year, natural fluctuations can be seen on top of this long-term warming. For this reason, scientists traditionally use a period of at least 30 years to identify a genuine climate trend.
Scientists are continually monitoring trends in climate, such as temperature, sea level, ocean heat, snow and ice. Often, several different research groups monitor the same issues, using different evaluation methods. When they reach a consensus, this gives added certainty to the trends. The trends across the range of climate metrics are consistent with a warming world.