Global warming
The long-term rise in global surface temperature, commonly measured against a pre-industrial baseline.
Example
A global average combines conditions over land and ocean. Local changes can be much larger or smaller.
The catch
A single hot year is different from a sustained warming level.
Related terms
Pre-industrial baseline, Albedo, Atmospheric lifetime, Carbon budget, Carbon dioxide, Climate change
In more depth
Global warming, explained.
Global warming is the temperature signal within climate change, which also covers shifts in rainfall, ice and extremes. Scientists build the global figure by combining land station records with sea-surface measurements and expressing each as a departure from a reference period, usually a pre-industrial baseline.
Warming is uneven. Land warms faster than the ocean, and the Arctic faster still. Year-to-year climate variability, such as El Niño, can lift or lower a single year without changing the trend. Assessments therefore describe warming levels as long-term averages. When you read that a threshold has been crossed, check whether the source means a month, a year or a sustained average, and which dataset and baseline it used.