Global surface temperature

In earth science, global surface temperature (GST; sometimes referred to as global mean surface temperature, GMST, or global average surface temperature) is calculated by averaging the temperature at the surface of the sea and air temperature over land. Periods of global cooling and global warming have alternated during Earth's history. of reliable global temperature measurements began in the 1850—1880 time frame. Through 1940, the average annual temperature increased, but was relatively stable between 1940 and 1975. Since 1975, it has increased by roughly 0.15 °C to 0.20 °C per decade, to at least 1.1 °C (1.9 °F) above 1880 levels. Sea levels have risen and fallen sharply during Earth's 4.6 billion year history. However, recent global sea level rise, driven by increasing global surface temperatures, has increased over the average rate of the past two to three thousand years. The continuation or acceleration of this trend will cause significant changes in the world's coastlines. In the 1860s, physicist John Tyndall recognized the Earth's natural greenhouse effect and suggested that slight changes in the atmospheric composition could bring about climatic variations. In 1896, a seminal paper by Swedish scientist Svante Arrhenius first predicted that changes in the levels of carbon dioxide in the atmosphere could substantially alter the surface temperature through the greenhouse effect. Changes in global temperatures over the past century provide evidence for the effects of increasing greenhouse gasses. When the climate system reacts to such changes, climate change follows. Measurement of the GST(global surface temperature) is one of the many lines of evidence supporting the scientific consensus on climate change, which is that humans are causing warming of Earth's climate system. Ocean heat content With the Earth's temperature increasing, the ocean has absorbed much of this increased heat, with the top 700 meters of ocean showing warming of 0.22 C (0.4 °F) since 1969. Expansion of the warm water, along with melting ice sheets, causes the sea level to rise.