Global and local warming

Climate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates. These changes have a broad range of observed effects that are synonymous with the term. Changes observed in Earth’s climate since the mid-20th century are driven by human activities, particularly fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth’s atmosphere, raising Earth’s average surface temperature. Natural processes, which have been overwhelmed by human activities, can also contribute to climate change, including internal variability (e.g., cyclical ocean patterns like El Niño, La Niña and the Pacific Decadal Oscillation) and external forcings (e.g., volcanic activity, changes in the Sun’s energy output, variations in Earth’s orbit). (Source: climate.nasa.gov)

Almost all climate experts agree that the mean temperature of the earth's surface everywhere on the planet raised of about 1,05 degrees C since the last decades of 1800 till today and that since 1980 occurred 24 of the hottiest years of this century and of 1900. 

Air mean temperature on earth was subject to natural oscillations in the last 150.000 years experimenting variations up to 6° C. Climate fluctuates over millenniums due to periodic changes in the emission of solar energy or due to alterations of the orbit and of the inclination of the earth's axis. Both factors influence the quantity and intensity of solar light that reaches the earth's surface. Maybe around 1860 when scientists begun recording the first reliable data our planet had not yet recovered from the little glacial era. Current global warming could be just an extension of this recovery.

In its rotation the Earth does not keep a steady position in its distance from the sun. In the 30ties serb mathematician Milutin Milankovitch said that 3 main alterations of the earth's movement influence climate: a cycle of 100.000 years in the planetary orbit, one of 41.000 years due to the inclination of the axis and another one of 23.000 years due to the oscillation of the axis. We could be in the middle of a long period of cooling. Cycles' effects are evident in the layers of ice (see graphic below) that grow when solar light reduces allowing snow to survive the thaw season and to heap up over time. 

Given that climate change is increasingly global but paradoxically more and more local due to cementation and consumption of forest and agricultural land resulting in "immediate" temperature rise through radiative unbalance, we are apt to believe as anticipated that 1989 was a sort of "borderline" year (or rather a stand-by one) during which temperature reached record values in the positive (from January to March, from late april until june and from late July to the end of year) and in the negative (early April and July) so that we can view it as a limit between the relative thermic normality experienced since 1951 and the drifting global warming of the end of XX century and the first 23 years of the new century. Examples (above) to corroborate this view are some recorded temperature records throughout the british isles during 1989 some of which (chiefly the negative ones) are still unsurpassed.