This is important because if we want to help the poor people who are most threatened by natural disasters, we have to recognize that it is less about cutting carbon emissions than it is about pulling them out of poverty.
The Intergovernmental Panel on Climate Change finds that "The poorest segments of societies are most vulnerable to climate change." Thus reducing the magnitude of climate change is integral to caring for the world's poor.
Yes, sea levels are rising, but the rise is not accelerating—if anything, two recent papers, one by Chinese scientists published in the January 2014 issue of Global and Planetary Change, and the other by U.S. scientists published in the May 2013 issue of Coastal Engineering, have shown a small decline in the rate of sea-level increase.
A more recent study published in January 2015 in the journal Nature found that the rate of sea level rise is actually increasing, from less than half and inch per decade from 1900-1990 to 1.2 inches per decade since 1990.
Of the large land areas where many people live, only the eastern portion of the United States recorded below-average temperatures in 2014, in sharp contrast to the unusual heat in the West.
Land areas are warming faster than oceans because of the larger capacity for water to absorb heat (IPCC AR5 Summary for Policy Makers http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_FINAL.pdf)
driving plants and animals to extinction,
"The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups." Carpenter et al., Science, 2008
Alternative energies are not necessarily economically inferior: http://www.bostonglobe.com/business/2014/11/24/renewable-energy-starts-win-price/1qaykTeSKnfZSf5UZoLwfN/story.html
In 2014 the extent of Arctic sea ice was larger than the minimum in 2006 but still 243,000 square miles less than the 1981-2000 average.
This timeseries figure from the National Snow and Ice Data Center (http://nsidc.org/arcticseaicenews/) shows that although there is year-to-year variability, the long term trend in sea ice extent is decreasing.
Although "natural" changes in solar irradiance can account for some of the warming since the Little Ice Age (Lean and Rind 1999, http://www.sciencedirect.com/science/article/pii/S1364682698001138 and Crowley 2000 http://www.sciencemag.org/content/289/5477/270.short), Crowley states that "the greenhouse effect has already established itself above the level of natural variability in the climate system" and Lean and Rind state that "while solar variability likely played a dominant role in modulating climate during the Little Ice Age prior to 1850, its influence since 1900 has become an increasingly less significant component of climate change in the industrial epoch. It is unlikely that Sun–climate relationships can account for much of the warming since 1970."
" 81 percent of Americans think global warming poses a serious problem in the United States. In addition, 81 percent think the federal government should limit the amount of greenhouse gases that American businesses can emit." Source: http://www.nytimes.com/2014/11/13/world/asia/in-climate-deal-with-china-obama-may-set-theme-for-2016.html?smprod=nytcore-ipad&smid=nytcore-ipad-share
Sheldon Whitehouse is a senator from Rhode Island, not New Hampshire
as hurricanes would shock the public. But the warming has leveled off since 1998, even as carbon-dioxide emissions have continued to rise, and hurricanes have gone quiet. “Where the heck is the warming,” one promine
Global climate models have difficulty accurately characterizing variability in the tropical Pacific (Jin et al. Climate Dynamics, 2008 http://link.springer.com/article/10.1007/s00382-008-0397-3), so if increased tradewinds in this region are the source of the warming hiatus, it is not surprising that global climate models have not accurately predicted it. This points to the need for a better representation of the tropical Pacific in global climate models, but does not indicate that warming due to greenhouse gases has ceased to be a problem.
This is not the first observed hiatus in warming: "A pause in surface warming in the mid-20th century coincided with increases in the atmospheric concentrations of sulfate aerosols, which are generally understood to cool the planet" (Clement and DiNezio, Science, 2014). Two recent studies point to decadal-scale natural variability in the tropical Pacific as a source of the recent hiatus: stronger trade winds expose more cool subsurface water, which is able to absorb more heat from the atmosphere (Kosaka et al., Nature, 2013 and Meehl et al., Journal of Climate, 2013).
This surprising fact demonstrates directly that natural influences and variability are powerful enough to counteract the present warming influence exerted by human activity.
The word counteract implies a logical connection between natural influences and human influences, which may not be the case at all.
The impact today of human activity appears to be comparable to the intrinsic, natural variability of the climate system itself.
In a study comparing human impacts and natural impacts on climate over the 20th century, Wigley and Santer write that "Our results show that the expected warming due to all human influences since 1950 (including aerosol effects) is very similar to the observed warming. Including the effects of natural external forcing factors has a relatively small impact on our 1950–2005 results..." in "A probabilistic quantification of the anthropogenic component of twentieth century global warming," (Climate Dynamics, 2013).
The most significant of these, published in Nature Geoscience by a team including 14 lead authors of the forthcoming IPCC scientific report, concluded that "the most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 degrees Celsius."
This is based on a single decade of relatively low temperatures and is not necessarily a good representation of ECS for the multidecadal timescales over which climate change is a concern.
Increased carbon dioxide levels also have caused and will continue to cause an increase in the growth rates of crops and the greening of the Earth—because plants grow faster and need less water when carbon dioxide concentrations are higher.
Taking into account increased heat stress, only C3 plants increase their photosynthesis under increased CO2 conditions.("A meta-analysis of plant physiological and growth responses to temperature and elevated CO2", Wang et. al., Oecologica 2012) When subjected to heat stress, C4 plants have a net reduction in photosynthesis. In addition according to a 2013 World Bank synthesis report, "The vulnerability of the agricultural sector to both climate change and variability is well established in the literature. The general consensus is that changes in temperature and precipitation will result in changes in land and water regimes that will subsequently affect agricultural productivity. Research has also shown that specifically in tropical regions, with many of the poorest countries, impacts on agricultural productivity are expected to be particularly harmful.(https://openknowledge.worldbank.org/handle/10986/16616)
Most experts believe that warming of less than 2 degrees Celsius from preindustrial levels will result in no net economic and ecological damage.
The AR5 SPM states, "Risks of global aggregate impacts are moderate for additional warming between 1-2°C, reflecting impacts to both Earth’s biodiversity and the overall global economy (medium confidence)." The statement in the article is not consistent with the AR5 statement. In addition, "Climate-change-related risks from extreme events, such as heat waves, extreme precipitation, and coastal flooding, are already moderate (high confidence) and high with 1°C additional warming (medium confidence)." "With increasing warming, some physical systems or ecosystems may be at risk of abrupt and irreversible changes. Risks associated with such tipping points become moderate between 0 - 1°C additional warming, due to early warning signs that both warm-water coral reef and Arctic ecosystems are already experiencing irreversible regime shifts (medium confidence)."
Still, the downward movement since 2007 is clear, especially at the bottom of the "likely" range.
Although there is a downward shift in the temperature rise projections, sea level rise predictions have increased from AR4 to AR5.
is "extremely likely" to be above 1 degree Celsius (1.8 degrees Fahrenheit), "likely" to be above 1.5 degrees Celsius (2.4 degrees Fahrenheit) and "very likely" to be below 6 degrees Celsius (10.8 Fahrenheit). In 2007, the IPPC said it was "likely" to be above 2 degrees Celsius and "very likely" to be above 1.5 degrees, with no upper limit. Since "extremely" and "very" have specific and different statistical meanings here, comparison is difficult.
In the AR5, "extremely likely" signifies a 95-100% probability. In both reports, "very likely" signifies a 90-100% probability. In AR5, "likely" signifies a 66-100% probability. Thus AR5 assigns a 66-100% probability that ECS is greater than 1.5C, and AR4 assigns this a 90-100% probability.
It is significant because it points to the very real possibility that, over the next several generations, the overall effect of climate change will be positive for humankind and the planet.
"Next several generations" is not a specific timeperiod, but we can assume this refers to the period of present-2100. The AR5 Summary for Policymakers (SPM) finds moderate risk of global aggregate impacts for the 1-2C temperature rise possible before 2100. Impacts will accelerate with increasing temperature.