What is climate?#
The terms “climate” and “weather” are often used interchangeably, but they hold distinctly different meanings for climate scientists.
Weather describes atmospheric conditions over short periods, typically spanning hours to days.
In contrast, climate refers to the average behavior of the atmosphere over much longer periods, ranging from years to decades, and sometimes even centuries. Typically, climatologists use a 30-year period as a standard to gather robust statistics and maintain stable climate conditions.
Between the scales of weather and climate change lies the concept of climate variability, also known as climate anomaly. This measures the deviations of a particular season’s or year’s condition from the climatological average for that period.
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The choice of data — whether focusing on weather, climate or climate variability — depends on the specific research question being addressed. For our drought analysis, we will consider only climate and climate variability data.
Tip
If you’re interested in this topic, sign up for the free “Climate Data Discovery – Introduction” course on the ECMWF eLearning website.
Climate variables and indicators#
What factors allow us to understand the climate and recognize changes in it?
An international panel of climate scientists has identified the 55 Essential Climate Variables (ECVs) grouped by components of the Earth system: atmosphere, land and oceans. Inside them we can find, for example, temperature, precipitation, greenhouse gases and fire. All these variables are constantly monitored to capture a detailed picture of Earth’s climate.
Global Climate Observing System
In addition to the essential variables, there are Climate Indicators, that show the long-term evolution of several key variables and are used to evaluate the global and regional trends of the climate. They are updated at least once a year.
Tip
To learn all about the ECVs and understand their purposes, visit the Global Climate Observing System (GCOS) website.
To know more about the Climate Indicators, have a look at the Copernicus/ECMWF page
