Climate

Quick facts about Climate

1. The word derives from the ancient Greek "klíma" (κλίμα), meaning "inclination" or "slope" referring to the tilt of the Earth's axis relative to the Sun, which early Greek geographers recognized determined regional solar exposure and weather patterns.
2. Under World Meteorological Organization (WMO) standards, "climate" is formally defined as the statistical mean and variability of atmospheric variables (temperature, precipitation, wind) calculated over a strict 30-year reference period to smooth out short-term annual weather anomalies.
3. Climate change is quantified through radiative forcing the net energy imbalance measured at the top of the atmosphere in watts per square meter ($W/m^2$). Current human greenhouse gas emissions exert a positive forcing of roughly +2.7 $W/m^2$, driving global heat absorption.
4. Earth's natural long-term climate shifts (ice ages and interglacials) are governed by three orbital cycles: eccentricity (orbit shape, ~100,000-year cycle), obliquity (axial tilt, ~41,000-year cycle), and precession (axial wobble, ~26,000-year cycle).
5. For the past 800,000 years, atmospheric $CO_2$ naturally oscillated between 180 ppm (glacial peaks) and 280 ppm (interglacials). Human activity breached 420 ppm, pushing $CO_2$ concentrations to levels unseen on Earth in over 3 million years.