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Older Peron warm and wet, global sea levels were 2.5 to 4 meters (8 to 13 feet) higher than the twentieth-century average 3900: 5.9 kiloyear event dry and cold. 3500: End of the African humid period, Neolithic Subpluvial in North Africa, expands Sahara Desert 3000 – 0: Neopluvial in North America 3,200–2,900: Piora Oscillation, cold
the Madden–Julian oscillation (MJO) – An eastward moving pattern of increased rainfall over the tropics with a period of 30 to 60 days, observed mainly over the Indian and Pacific Oceans. [ 28 ] the North Atlantic oscillation (NAO) – Indices of the NAO are based on the difference of normalized sea-level pressure (SLP) between Ponta ...
World Storytelling Day is a global celebration of the art of oral storytelling, celebrated every year on the day of the northward equinox. [citation needed] World Citizen Day occurs on the northward equinox. [30] The Baháʼí calendar year starts at the sunset preceding the March equinox calculated for Tehran. [31]
By far the best observed period is from 1850 to the present day, with coverage improving over time. Over this period the recent instrumental record, mainly based on direct thermometer readings, has approximately global coverage. It shows a general warming in global temperatures. Before this time various proxies must be used.
Climate (from Ancient Greek κλίμα ' inclination ') is commonly defined as the weather averaged over a long period. [9] The standard averaging period is 30 years, [10] but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations.
The remaining 0.9 to 1.0 ‰ was due to about 5 to 6 °C (9 to 10 °F) of global cooling. [32] The transition likely took place in three closely spaced steps over the period from 33.8 to 33.5 mya. By the end of the transition, sea levels had dropped by 105 meters (344 ft), and ice sheets were 25% greater in extent than in the modern world. [38]
A less severe cold period or ice age is shown during the Jurassic-Cretaceous (150 Ma). There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation , in progress since 2.58 million years ago.
Records of global average surface temperature are usually presented as anomalies rather than as absolute temperatures. A temperature anomaly is measured against a reference value (also called baseline period or long-term average). [42] Usually it is a period of 30 years. For example, a commonly used baseline period is 1951-1980.