Climate Climate Change in Portugal

What is Climate?

Climate, sometimes understood as the "average weather”, is defined as the measurement of the mean and variability of relevant quantities of certain variables (such as temperature, precipitation or wind) over a period of time, ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). Climate in a wider sense is the state, including a statistical description, of the climate system.

What is difference between weather and climate?

Some people say "weather you are observed" and "climate you are expected." "Weather" refers to more local changes that we see around us on short time frames from minutes to hours or days to weeks. Familiar examples are the rain, snow, clouds, wind, storms, heat waves and floods. "Climate" refers to long-term average (which may be regional or global), and can be thought of as the time averaged over several seasons, years or decades. Climate change is more difficult for us to have a sense because the deadlines involved are much longer, and the impact of climate change may be less immediate. Examples of climate change include several drier summers than normal, winters smoother from childhood of our grandparents to our days or other variations caused by, for example, El Niño or La Niña events.

What is Climate Change?

Climate change refers to a statistically significant variation in either the mean state of the climate or in it's variability, persisting for an extended period (typically decades or longer). 

Climate change may be due to natural internal processes or external factors such as persistent changes to the atmosphere or changes on land use. 

Article 1 of the the United Nations Framework Convention on Climate Change (UNFCCC) defines "climate change" as: "a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”

The UNFCCC thus makes a distinction between "climate change" attributable to human activities altering the atmospheric composition, and "climate variability" attributable to natural causes.

What is Climate System?

The climate system consists of five major components; the atmosphere, the biosphere, the cryosphere, the hydrosphere and land surface. The climate system is continually changing due to the interactions among the components as well as external factors such as solar variations or volcanic eruptions and human induced factors such as changes to the atmosphere and changes on land use.

Why to use Rotate Grid?

Rotate Grids are used to avoid problem of decreasing linear distances along nearest pole longitudes. As approach near poles spacing of the horizontal grid decreases, causing numerical instabilities in analyzes. Many weather  prediction models using gratings with arbitrary north pole, which differs from the geographic pole.