Fifteen thousand Parisians are estimated to have died from heat in August, , along with thousands of farm animals. For the study, Meehl and Tebaldi compared present and future decades to determine how greenhouse gases and sulfate aerosols might affect future climate in Europe and the United States, focusing on Paris and Chicago.
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They assumed little policy intervention to slow the buildup of greenhouse gases. During the Paris and Chicago heat waves, atmospheric pressure rose to values higher than usual over Lake Michigan and Paris, producing clear skies and prolonged heat. In the model, atmospheric pressure increases even more during heat waves in both regions as carbon dioxide accumulates in the atmosphere. Heat wave is based on the concept of exceeding specific thresholds, thus allowing analyses of heat wave duration and frequency. Three criteria were used to define heat waves in this way, which relied on two location-specific thresholds for maximum temperatures.
Threshold 1 T1 was defined as the A heat wave was then defined as the longest period of consecutive days satisfying the following three conditions:. Because the Chicago heat wave of and the Paris heat wave of had particularly severe impacts, we chose grid points from the model that were close to those two locations to illustrate heat wave characteristics.
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This choice was subjective and illustrative given that there are, of course, other well-known heat waves from other locations. Also, we are not suggesting that a model grid point is similar to a particular weather station; we picked these grid points because they represent heat wave conditions for regions representative of Illinois and France in the model, and therefore they can help identify processes that contribute to changes in heat waves in the future climate in those regions. Heat waves in Chicago, Paris, and elsewhere in North America and Europe will become more intense, more frequent and longer lasting in the 21st century, according to a new modeling study by two scientists at the National Center for Atmospheric Research NCAR in Boulder, Colo.
In the United States, heat waves will become most severe in the West and South. The findings appear in the August 13 issue of the journal Science. Department of Energy DOE. During the Chicago heat wave, the most severe health impacts resulted from the lack of cooling relief several nights in a row, according to health experts.
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In the model, the western and southern United States and the Mediterranean region of Europe experience a rise in nighttime minimum temperatures of more than 3 degrees Celsius 5. They will occur more often: The average number of heat waves in the Chicago area increases in the coming century by 25 percent, from "Heat Waves of the 21st Century: More Intense, More Frequent and Longer Lasting. In Paris, the average number increases 31percent, from 1. They will last longer: Chicago's present heat waves last from 5.
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In Paris, present-day heat waves persist from 8. Source: National Science Foundation. Based on tide gauge data, the rate of global mean sea level rise during the 20th century is in the range 1. The causes for change of the sea level : At the shoreline it is determined by many factors in the global environment that operate on a great range of time-scales, from hours tidal to millions of years ocean basin changes due to tectonics and sedimentation. On the time-scale of decades to centuries, some of the largest influences on the average levels of the sea are linked to climate and climate change processes.
Firstly, as ocean water warms, it expands.
On the basis of observations of ocean temperatures and model results, thermal expansion is believed to be one of the major contributors to historical sea level changes. Further, thermal expansion is expected to contribute the largest component to sea level rise over the next hundred years. Deep ocean temperatures change only slowly; therefore, thermal expansion would continue for many centuries even if the atmospheric concentrations of greenhouse gases were to stabilise.
Study of Impacts of Global Warming on Climate Change: Rise in Sea Level and Disaster Frequency
The amount of warming and the depth of water affected vary with location. In addition, warmer water expands more than colder water for a given change in temperature. The geographical distribution of sea level change results from the geographical variation of thermal expansion, changes in salinity, winds, and ocean circulation.
reqegycavy.gq The range of regional variation is substantial compared with the global average sea level rise. Rise in sea Level: Sea level also changes when the mass of water in the ocean increases or decreases. This occurs when ocean water is exchanged with the water stored on land. The major land store is the water frozen in glaciers or ice sheets. Indeed, the main reason for the lower sea level during the last glacial period was the amount of water stored in the large extension of the ice sheets on the continents of the Northern Hemisphere.
After thermal expansion, the melting of mountain glaciers and ice caps is expected to make the largest contribution to the rise of sea level over the next hundred years. These glaciers and ice caps make up only a few per cent of the world's land-ice area, but they are more sensitive to climate change than the larger ice sheets in Greenland and Antarctica, because the ice sheets are in colder climates with low precipitation and low melting rates. Consequently, the large ice sheets are expected to make only a small net contribution to sea level change in the coming decades.
A new study says the seas are acidifying ten times faster today than 55 million years ago when a mass extinction of marine species occurred. And, the study concludes, current changes in ocean chemistry due to the burning of fossil fuels may portend a new wave of die-offs. In other words, the vast clouds of shelled creatures in the deep oceans had virtually disappeared. The seawater became so corrosive that it ate away at the shells, along with other species with calcium carbonate in their bodies. It took hundreds of thousands of years for the oceans to recover from this crisis, and for the sea floor to turn from red back to white.
By spewing carbon dioxide into the air, we are now once again making the oceans more acidic. Approximately one millennium after the 7 Ka 32 nd Century BCE slowing of sea-level rise, many coastal urban centers rose to prominence around the world Day, John W. It has been hypothesized that this is correlated with the development of stable coastal environments and ecosystems and an increase in marine productivity also related to an increase in temperatures , which would provide a food source for hierarchical urban societies. The last written records of the Norse Greenlanders are from a marriage in the church of Hvalsey — today the best-preserved of the Norse ruins.
Climate change has been associated with the historical collapse of civilizations, cities and dynasties.
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Notable examples of this include the Anasazi Demenocal, P. Other, smaller communities such as the Viking settlement of Greenland transl. There are two proposed methods of Classic Maya collapse: environmental and non-environmental. The environmental approach uses paleoclimatic evidence to show that movements in the intertropical convergence zone likely caused severe, extended droughts during a few time periods at the end of the archaeological record for the classic Maya Haug, Gh, et al.
The non-environmental approach suggests that the collapse could be due to increasing class tensions associated with the building of monumental architecture and the corresponding decline of agriculture Hosler D, et al. The Harappa and Indus civilizations were affected by drought 4,—3, years ago.
Notable periods of climate change in recorded history include the medieval warm period and the little ice age. In the case of the Norse, the medieval warm period was associated with the Norse age of exploration and arctic colonization, and the later colder periods led to the decline of those colonies Patterson, W. Climate change in the recent past may be detected by corresponding changes in settlement and agricultural patterns. Archaeological evidence, oral history and historical documents can offer insights into past changes in the climate.
Climate change effects have been linked to the collapse of various civilizations. The instrumental temperature record shows global warming of around 0. The future level of global warming is uncertain, but a wide range of estimates projections have been made Fisher, BS et al. Climate models using the six SRES "marker" scenarios suggest future warming of 1.
The projected rate of warming under these scenarios would very likely be without precedent during at least the last 10, years IPCC SPM. The most recent warm period comparable to these projections was the mid-Pliocene, around 3 million years ago Stern N.
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Global Land-Ocean, mean surface temperature difference from the average for — Courtesy: Wikipedia. The most recent report IPCC projected that during the 21st century the global surface temperature is likely to rise a further1. This was based on the consistency of evidence across a range of observed changes, including increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level Solomon S, b.
Human activities have contributed to a number of the observed changes in climate Hegerl GC, et. This contribution has principally been through the burning of fossil fuels, which has led to an increase in the concentration of GHGs in the atmosphere. This increase in GHG concentrations has caused a radiative forcing of the climate in the direction of warming. Human-induced forcing of the climate has likely to contributed to a number of observed changes, including sea level rise, changes in climate extremes such as warm and cold days , declines in Arctic sea ice extent, and to glacier retreat Fig.