The Climate Bet site was originally created to chronicle Scott Armstrong's $20, Global Warming Challenge to Al Gore to provide better forecasts than the no-change model. While the challenge still stands, The site now promotes the use of proper scientific forecasting methods for long-term global climate change policy. blogger.com Jan 22, · That humans are causing global warming is the position of the Academies of Science from 19 countries plus many scientific organizations that study climate science. More specifically, around 95% of active climate researchers actively publishing climate papers endorse the consensus position Dec 13, · The extent of the human contribution to modern global warming is a hotly debated topic in political circles, particularly in the US. During a recent congressional hearing, Rick Perry, the US energy secretary, remarked that “to stand up and say that % of global warming is because of human activity, I think on its face, is just indefensible”
The 97% consensus on global warming
The extent of the human contribution to modern global warming is a hotly debated topic in political circles, particularly in the US. However, the science on the human contribution to modern warming is quite clear. To assess the role of each different forcing in observed temperature changes, Carbon Brief adapted a simple statistical climate model developed by Dr Karsten Haustein and his colleagues at the University of Oxford and University of Leeds. This model finds the relationship between both human and natural climate forcings and temperature that best matches observed temperatures, both globally and over land areas only.
Global warming term papers figure below shows the estimated role of each different climate forcing in changing global surface temperatures since records began in — including greenhouse gases red lineaerosols dark blueland use light blueozone pinksolar yellow and volcanoes orange.
The black dots show observed temperatures from the Berkeley Earth surface temperature project, while the grey line shows the estimated warming from the combination of all the different types of forcings.
The combination of all radiative forcings generally matches longer-term changes in observed temperatures quite well. There is some year-to-year variability, primarily from El Niño eventsglobal warming term papers, that is not driven by changes in forcings.
There are also periods from and where some larger disagreements are evident between projected and observed warming, both in this simple model and in more complex climate models. The chart highlights that, of all the radiative forcings analysed, only increases in greenhouse gas emissions produce the magnitude of warming experienced over the past years, global warming term papers. If greenhouse gas emissions alone were warming the planet, we would expect to see about a third more warming than has actually occurred.
The extra warming from greenhouse gases is being offset by sulphur dioxide and other products of fossil fuel combustion that form atmospheric aerosols. Aerosols in the atmosphere both reflect incoming solar radiation back into space and increase the formation of high, reflective clouds, cooling the Earth. Ozone is a short-lived greenhouse gas that traps outgoing heat and warms the Earth.
Ozone is not emitted directly, but is formed when methane, carbon monoxide, nitrogen oxides and volatile organic compounds break down in the atmosphere. Increases in ozone are directly attributable to human emissions of these gases, global warming term papers. In the upper atmosphere, reductions in ozone associated with chlorofluorocarbons Global warming term papers and other halocarbons depleting the ozone layer have had a modest cooling effect. The net effects of combined global warming term papers and upper atmospheric ozone global warming term papers have modestly warmed the Earth by a few tenths of a degree.
For example, replacing a forest with a field will generally increase the amount of sunlight reflected back into space, particularly in snowy regions. The net climate effect of land-use changes since is a modest cooling. Volcanoes have a short-term cooling effect on the climate due to their injection of sulphate aerosols high into the stratosphere, where they can remain aloft for a few years, reflecting incoming sunlight back into space.
However, once the sulphates drift back down to the surface, global warming term papers, the cooling effect of volcanoes goes away. The orange line shows the estimated impact of volcanoes on the climate, with large downward spikes in temperatures of up to 0. Finally, solar activity is measured by satellites over the past few decades and estimated based on sunspot counts in the more distant past. The amount of energy reaching the Earth from the sun fluctuates modestly on a cycle of around 11 years.
There has been a slight increase in overall solar activity since the s, but the amount of additional solar energy reaching the Earth is small compared to other radiative forcings examined. Over the past global warming term papers years, solar energy reaching the Earth has actually declined slightlywhile temperatures have increased dramatically. The accuracy of this model depends on the accuracy of the radiative forcing estimates. Some types of radiative forcing like that from atmospheric CO2 concentrations can be directly measured and have relatively small uncertainties.
Others, such as aerosols, are subject to much greater uncertainties due to the difficulty of accurately measuring their global warming term papers on cloud formation. These are accounted for in the figure below, which shows combined natural forcings blue line and human forcings red line and the uncertainties that the statistical model associates with each. These shaded areas are based on different estimates of radiative forcings, incorporating research attempting to estimate a range of values for each.
Uncertainties in human factors increase afterdriven largely by increases in aerosol emissions after that point. Global mean surface temperatures from Berkeley Earth black dots and modelled influence of all combined natural blue line and human red line radiative forcings with their respective uncertainties shaded areas for the period from global warming term papers The combination of all natural and human forcings grey line is also shown.
See methods at the end of the global warming term papers for details. Chart by Carbon Brief using Highcharts. Combined natural forcings show a modest cooling, primarily driven by global warming term papers eruptions. The simple statistical model used for this analysis by Carbon Brief differs from much more complex climate models generally used by scientists to assess the human fingerprint on warming, global warming term papers.
Climate models also include variations in temperature over space and time, and can account for different efficacies of radiative forcings in different regions of the Earth. However, when analysing the impact of different forcings on global temperatures, complex climate models generally find results similar to simple statistical models.
Observed temperatures are shown in black, while the sum of human forcings is shown in orange. The IPCC also included the estimated magnitude of internal variability over that period in the models, which they suggest is relatively small and comparable to that of natural forcings. Land temperatures have warmed considerably faster than average global temperatures over the past century, with temperatures reaching around 1. The land temperature record also goes back further in time than the global temperature record, though the period prior to is subject to much greater uncertainties.
Both global warming term papers and natural radiative forcings can be matched to land temperatures using the statistical model. The magnitude of human and natural forcings will differ a bit between land and global temperatures. For example, global warming term papers, volcanic eruptions appear to have a larger influence on land, as land temperatures are likely to respond faster to rapid changes in forcings. The figure below shows the relative contribution of each different radiative forcing to land temperatures since Land mean surface temperatures from Berkeley Earth black global warming term papers and modeled influence of different radiative forcings colored linesglobal warming term papers, as well as the combination of all forcings grey line for the period from to The combination of all forcings generally matches observed temperatures quite well, with short-term variability around the grey line primarily driven by El Niño and La Niña events, global warming term papers.
There is a wider variation in temperatures prior toreflecting the much larger uncertainties in the observational records that far back. There is still a period around and where observations exceed what the model predicts, though the differences are less pronounced than in global temperatures and the divergence is mostly absent in land records.
Volcanic eruptions in the late s global warming term papers early s stand out sharply in the land record. The eruption of Mount Tambora in Indonesia in may have cooled land temperatures by a massive 1. In general, volcanoes appear to cool land temperatures by nearly twice as much as global temperatures.
Carbon Brief used the same model to project future temperature changes associated with each forcing factor. The figure below shows observations up toalong with future post radiative forcings from RCP6. Global mean surface temperatures from Berkeley Earth black dots and modeled influence of different radiative forcings colored lines for the period from to Forcings post taken from RCP6.
When provided with the radiative forcings for the RCP6. Future radiative forcing from CO2 is expected to continue to increase if emissions rise. This reduction in aerosols will enhance overall warming, bringing total warming from all radiative forcing closer to warming from greenhouse gases alone.
The RCP scenarios assume no specific future volcanic eruptions, as the timing of these is unknowable, while solar output continues its year cycle. This approach can also be applied to land temperatures, as shown in the figure below. Here, land temperatures are shown between andwith post forcings also from RCP6.
Land mean surface temperatures from Berkeley Earth black dots and modeled influence of different radiative forcings colored lines for the period from to This is seen in the model results, global warming term papers, where land warms by around 4C by compared to 3C globally in the RCP6.
There is a wide range of future warming possible from different RCP scenarios and different values for the sensitivity of the climate systembut all show a similar pattern of declining future aerosol emissions and a larger role for greenhouse gas forcing in future temperatures. While natural forcings from solar and volcanoes do not seem to play much of a role in global warming term papers warming, there is also natural variability associated with ocean cycles and variations in ocean heat uptake.
As the vast majority of energy trapped by global warming term papers gases is absorbed by the oceans rather than the atmosphere, changes in the rate of ocean heat uptake can potentially have large impacts on the surface temperature.
Some researchers have argued that multidecadal cycles, such as the Atlantic Multidecadal Oscillation AMO and Pacific Decadal Oscillation PDOcan play a role in warming at a decadal scale. While human factors explain all the long-term warming, there are some specific periods that appear to have warmed or cooled faster than can be explained based on our best estimates of radiative forcing. For example, the modest mismatch between the radiative forcing-based estimate and observations during the mids might be evidence of a role for natural variability during that period.
A number of researchers have examined the potential for natural variability to impact long-term warming trends. They have found that it generally plays a limited role. But that is a weak argument: you can, of course, never rule out the unknown unknown. The question is whether there is strong, global warming term papers, or even any evidence for it.
And the answer is no, in my view. Models get the short-term temperature variability approximately right. In many cases, they even have too much. But the forced response pretty much explains the observations, so there is no evidence from the 20th century that we are missing something….
Similarly, Dr Martin Stolpe and colleagues, also at IAC, recently analysed the role of multidecadal natural variability in both the Atlantic and Pacific oceans. Internal variability is likely to have a much global warming term papers role in regional temperatures. For example, in producing unusually warm periods in the Arctic and the US in the s. However, its role in influencing long-term changes in global surface temperatures appears to be limited, global warming term papers.
The global warming witnessed over the past years matches nearly perfectly what is expected from greenhouse gas emissions and other human activity, both in the simple model examined global warming term papers and in more complex climate models.
Some uncertainty remains due to the role of natural variability, global warming term papers, but researchers suggest that ocean fluctuations and similar factors are unlikely to be the cause of more than a small fraction of modern global warming. The simple statistical model used in this article is adapted global warming term papers the Global Warming Index published by Haustein et al In turn, it is based on the Otto et al model.
The model estimates contributions to observed climate change and removes the impact of natural year-to-year fluctuations by a multiple linear regression of observed temperatures and estimated responses to total human-induced and total natural drivers of climate change. The forcing responses are provided by the standard simple climate model given in Chapter 8 of IPCCbut the size of these responses is estimated by the fit to the observations.
The forcings are based on IPCC values and were updated to using data from NOAA and ECLIPSE. Piers Forster of the University of Leedsglobal warming term papers, reflecting the uncertainty in forcing estimates.
An Excel spreadsheet containing their model is also provided. The model was adapted by calculating forcing responses for each of the different major climate forcings rather than simply total human and natural forcings, global warming term papers, using the Berkeley Earth record for observations.
The decay time of thermal response used in converting forcings to forcing responses was adjusted to be one year rather than four years for volcanic forcings to better reflect the fast response time present in observations. The effects of El Niño and La Niña ENSO events was removed from the observations using an approach adapted from Foster and Rahmstorf and the Kaplan El Niño 3. The temperature response for each individual forcing was calculated by scaling their forcing responses by the total human or natural coefficients from the regression model.
Global Warming Research Paper
, time: 1:33The Name Game: From “Global Warming” to “Climate Change”
Global Warming Definition: "Global warming is a consistent upsurge in the earth's average temperature denoted by increasing global surface temperatures caused or influenced by the uninterrupted emissions of greenhouse gases, over 90% of the air getting polluted by carbon dioxide and CFCs like Methane and Nitrous oxide and other air pollutants affecting the climate sensitivity and levels of The Climate Bet site was originally created to chronicle Scott Armstrong's $20, Global Warming Challenge to Al Gore to provide better forecasts than the no-change model. While the challenge still stands, The site now promotes the use of proper scientific forecasting methods for long-term global climate change policy. blogger.com Dec 14, · Global warming has reached a level such that we can ascribe with a high degree of confidence a cause-and-effect relationship between the greenhouse effect and the observed warming. How we went from “global warming” to “climate change,” however, is less clear. Within scientific journals, there is a difference between “climate change
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