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Sudden Climate Change
An abrupt climate change occurs when the climate system is forced to transition at a rate that is determined by the climate system energy-balance. The transition rate is more rapid than the rate of change of the external forcing, though it may include sudden forcing events such as meteorite impacts. Abrupt climate change therefore is a variation beyond the variability of a climate. Past events include the end of the Carboniferous Rainforest Collapse, Younger Dryas, Dansgaard–Oeschger events, Heinrich events and possibly also the Paleocene–Eocene Thermal Maximum. The term is also used within the context of climate change to describe sudden climate change that is detectable over the time-scale of a human lifetime. Such a sudden climate change can be the result of feedback loops within the climate system or tipping points in the climate system. Scientists may use different timescales when speaking of ''abrupt events''. For example, the duration of the onset of the Paleocene� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenhouse Gas Emissions
Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate change. The top contributors to greenhouse gas emissions, largest annual emissions are from China followed by the United States. The United States has List of countries by greenhouse gas emissions per capita, higher emissions per capita. The main producers fueling the emissions globally are Big Oil, large oil and gas companies. Emissions from human activities have increased Carbon dioxide in Earth's atmosphere, atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than any decade before. Total cumulative emissions from 1870 to 2022 were 703 (2575 ), of which 484±20 (177 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Before Present
Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1January 1950 as the commencement date (epoch) of the age scale, with 1950 being labelled as the "standard year". The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must account for when using radiocarbon dating for dates of origin that may fall after this year. In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation "RCYBP" stands for the explicit "radio carbon years before present". Usage The BP scale is s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Cold Reversal
The Antarctic Cold Reversal (ACR) was a climatic event of intense atmospheric and oceanic cooling across the southern hemisphere (>40°S) between 14,700 and 13,000 years before present ( BP) that interrupted the most recent deglacial climate warming (c. 18,000-11,500 years BP). This cooling event was initially well noted in Antarctic ice core records. Soon after, evidence from sediment cores and glacial advances from land masses (southern South America, New Zealand, Tasmania, among others) and Oceanic sectors south of 40°S expanded the region of this climate cooling event. The ACR illustrates the complexity of the climate changes at the transition from the Pleistocene to the Holocene Epochs. In general, climate models show a 1.5-2 °C drop in Antarctica and other temperate regions where glacial readvances are typically evident. Climate continued to warm after 13,000 years BP and glaciers showed signs of abrupt withdrawal from their respective ACR aged moraines. The mechanisms b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacial Lake Agassiz
Lake Agassiz ( ) was a large proglacial lake that existed in central North America during the late Pleistocene, fed by meltwater from the retreating Laurentide Ice Sheet at the end of the last glacial period. At its peak, the lake's area was larger than all of the modern Great Lakes combined. It eventually drained into what is now Hudson Bay, leaving behind Lake Winnipeg, Lake Winnipegosis, Lake Manitoba, and Lake of the Woods. First postulated in 1823 by William H. Keating, it was named by Warren Upham in 1879 after Louis Agassiz, the then recently deceased (1873) founder of glaciology, when Upham recognized that the lake was formed by glacial action. Geological progression During the last glacial maximum, northern North America was covered by an ice sheet, which alternately advanced and retreated with variations in the climate. This continental ice sheet formed during the period now known as the Wisconsin glaciation, and covered much of central North America between 30,0 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ocean Acidification
Ocean acidification is the ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ocean acidification, with Carbon dioxide in Earth's atmosphere, atmospheric carbon dioxide () levels exceeding 422 ppm (). from the atmosphere is absorbed by the oceans. This chemical reaction produces carbonic acid () which dissociates into a bicarbonate ion () and a hydrogen ion (). The presence of free hydrogen ions () lowers the pH of the ocean, increasing acidity (this does not mean that seawater is acidic yet; it is still alkaline, with a pH higher than 8). Marine biogenic calcification, Marine calcifying organisms, such as Mollusca, mollusks and corals, are especially vulnerable because they rely on calcium carbonate to build shells and skeletons. A change in pH by 0.1 represents a 26% increase in hydrogen ion concentration in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clathrate Gun Hypothesis
The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature, as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years, and 25 times over 100 years (33 when accounting for aerosol interactions). It is further proposed that these warming events caused the Bond event, Bond cycles and individual interstadial events, such as the Dansgaard–Oeschger event, Dansgaard–Oeschger interstadials. The hypothesis was supported for the Bølling–Allerød warming and Preboreal periods, but not for Dansgaar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermohaline Circulation
Thermohaline circulation (THC) is a part of the large-scale Ocean current, ocean circulation driven by global density gradients formed by surface heat and freshwater fluxes. The name ''thermohaline'' is derived from ''wikt:thermo-, thermo-'', referring to temperature, and ', referring to salinity, salt content—factors which together determine the Water (molecule)#Density of saltwater and ice, density of sea water. Wind-driven surface currents (such as the Gulf Stream) travel Polar regions of Earth, polewards from the equatorial Atlantic Ocean, cooling and sinking en-route to higher latitudes - eventually becoming part of the North Atlantic Deep Water - before flowing into the ocean basins. While the bulk of thermohaline water upwelling, upwells in the Southern Ocean, the oldest waters (with a transit time of approximately 1000 years) upwell in the North Pacific; extensive mixing takes place between the ocean basins, reducing the difference in their densities, forming the Worl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature (journal)
''Nature'' is a British weekly scientific journal founded and based in London, England. As a multidisciplinary publication, ''Nature'' features Peer review, peer-reviewed research from a variety of academic disciplines, mainly in science and technology. It has core editorial offices across the United States, continental Europe, and Asia under the international scientific publishing company Springer Nature. ''Nature'' was one of the world's most cited scientific journals by the Science Edition of the 2022 ''Journal Citation Reports'' (with an ascribed impact factor of 50.5), making it one of the world's most-read and most prestigious academic journals. , it claimed an online readership of about three million unique readers per month. Founded in the autumn of 1869, ''Nature'' was first circulated by Norman Lockyer and Alexander MacMillan (publisher), Alexander MacMillan as a public forum for scientific innovations. The mid-20th century facilitated an editorial expansion for the j ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Core
An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires .... Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ice formed over a range of years. Cores are Ice drilling, drilled with hand Auger (drill), augers (for shallow holes) or powered drills; they can reach depths of over two miles (3.2 km), and contain ice up to 800,000 years old. The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogen isotopes provide information about Paleothermometer, ancient temperatures, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleoclimatology
Paleoclimatology ( British spelling, palaeoclimatology) is the scientific study of climates predating the invention of meteorological instruments, when no direct measurement data were available. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to understand natural variation and the evolution of the current climate. Paleoclimatology uses a variety of proxy methods from Earth and life sciences to obtain data previously preserved within rocks, sediments, boreholes, ice sheets, tree rings, corals, shells, and microfossils. Combined with techniques to date the proxies, the paleoclimate records are used to determine the past states of Earth's atmosphere. The scientific field of paleoclimatology came to maturity in the 20th century. Notable periods studied by paleoclimatologists include the frequent glaciations that Earth has undergone, rapid cooling events like the Younger Dryas, and the rapid warming du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
