“Climate” is distinguished from “weather”, in that weather is the day-to-day state of the atmosphere and environment, whereas climate is the statistical average of weather patterns over a limited region and a long period (usually, minimum 30 years). A number factors have some influence on variations in the climate in the various regions or zones of the Earth – but it must be noted that none of these changes work (or actually initiate themselves) in isolation.
The natural climatic systems of the Earth are primarily determined by a dynamic complex of linkages, synergies and interactions among the processes, components and sub-systems of the atmosphere, hydrosphere, lithosphere and biosphere. The hydrosphere in this context includes all of the Earth’s water – oceans, rivers, lakes and the cryosphere (ice caps and snow). The main variables which characterize climate are temperature and precipitation (rainfall), humidity and cloudiness (special disturbances such as droughts and hurricanes are sometimes included). These elements are in turn dependent on the meteorological variables (of weather) – such as insolation (solar radiation), wind speed and direction, ocean surface temperature, etc. To this must be added the variability of the Sun’s radiation and the Earth’s orbit, which result in an extremely complex and dynamic system.
Thus the climate system is a global complex of linkages and interactions. Spatial variations of all scales exist from the very large scale (e.g., 10,000 km) to the very small scale (e.g., 1 mm). This complex system is acted upon by a range of stimuli associated with the Sun, the Moon, and the Earth’s orbit around the sun. The main factors affecting climate change (natural variability) include: (1) Diurnal oscillations, due to the Earth’s rotation; (2) Tidal oscillations, due to gravitational effects of the Sun and Moon, with main periods of 12.4 hr and 24.8 hr; (3) Seasonal oscillations, due to the inclination of the equator to the ecliptic, and to changes in Sun-Earth distance; (4) Synoptic oscillations, caused by Rossby waves, with scales of 1000 km and periods of days; (5) Global oscillations with periods from weeks to months; (6) Inter-annual oscillations with periods ranging from 2 to 5 years, including El Niño/La Niña phenomena in the Pacific; and (7) Secular or long period oscillations with periods ranging from years to tens of thousands of years (the ice ages), likely due to orbital variations.
Having established the above – one of the main issues in the current debate is the possible effects of human industrial and other activities on the global climate. Despite the assertions in some quarters, anthropogenic effects are for the Moment much smaller than these natural effects, the main concern being time-scales – their effects are felt within lifetimes rather than thousands of years. The critical point, is that many of the factors (“forcers” and “reactors”) in our current environment never existed in the past – many of the culprits (such as CFC) do not occur freely in nature, further to which, the rate of change of the release of naturally occurring greenhouse gases (such as carbon dioxide) over the past 200 yr or so (since the “industrial revolution”) is unprecedented and likely a result of human activities (such as deforestation). While, it is very true that global warming and climate change are a natural process on the Earth; the main issue is that the new or additional parameters added by human activities make it very difficult to use past cycles of “Ice Ages” and “Tropical Ages” to predict what is to be expected. Even if our activities are much less significant than natural variations (in the global context), they definitely are not helping the situation. Environmental changes by human activities also affect the micro-climate in which we live, on an obviously much shorter time-scale.