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Reconstruction of the past 5 million years of climate history, based on oxygen isotope fractionation in deep sea sediment cores (serving as a proxy for the total global mass of glacial ice sheets), fitted to a model of orbital forcing (Lisiecki and Raymo 2005) [2] and to the temperature scale derived from Vostok ice cores following Petit et al. (1999).
Projected global surface temperature changes relative to 1850–1900, based on CMIP6 multi-model mean changes. The IPCC Sixth Assessment Report defines global mean surface temperature (GMST) as the "estimated global average of near-surface air temperatures over land and sea ice, and sea surface temperature (SST) over ice-free ocean regions, with changes normally expressed as departures from a ...
500 million years of climate change Ice core data for the past 400,000 years, with the present at right. Note length of glacial cycles averages ~100,000 years. Blue curve is temperature, green curve is CO 2, and red curve is windblown glacial dust (loess). Scale: Millions of years before present, earlier dates approximate.
The IPCC Fifth Assessment Report (AR5 WG1) of 2013 examined temperature variations during the last two millennia, and cited the following reconstructions in support of its conclusion that for average annual Northern Hemisphere temperatures, "the period 1983–2012 was very likely the warmest 30-year period of the last 800 years (high confidence ...
The Cretaceous Thermal Maximum (CTM), also known as Cretaceous Thermal Optimum, was a period of climatic warming that reached its peak approximately 90 million years ago (90 Ma) during the Turonian age of the Late Cretaceous epoch. The CTM is notable for its dramatic increase in global temperatures characterized by high carbon dioxide levels.
According to IPCC Sixth Assessment Report, in the last 170 years, humans have caused the global temperature to increase to the highest level in the last 2,000 years. The current multi-century period is the warmest in the past 100,000 years. [3] The temperature in the years 2011-2020 was 1.09 °C higher than in 1859–1890.
Reconstructions of global temperature of the past 2000 years, using composite of different proxy methods. In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements [1] and enable scientists to reconstruct the climatic conditions over a longer fraction of the Earth's history.
The stacked record of the 57 cores was orbitally tuned to an orbitally driven ice model, the Milankovitch cycles of 41 ky , 26 ky and 100 ky (eccentricity), which are all assumed to cause orbital forcing of global ice volume. Over the past million years, there have been a number of very strong glacial maxima and minima, spaced by roughly 100 ky.