The End of Doom

by Ronald Bailey

  The Nature Geoscience estimate is a whole degree lower than the best estimate calculated by the IPCC in 2007. Interestingly, the 2013 Physical Science report, unlike its predecessor reports, provides no best estimate of climate sensitivity. Research on this topic continues. For example, in a March 2014 study, Norwegian researchers take into account the last ten years of temperature records and trends in ocean heat buildup. Their estimates for climate sensitivity and transient climate response are even lower. They report that the best estimate of climate sensitivity “is 1.8°C, with 90% C.I. [confidence interval], ranging from 0.9 to 3.2°C, which is tighter than most previously published estimates.” They also calculate that there is only 1.4 percent chance that climate sensitivity would turn out to be greater than 4.5°C. Since the amount of warming that a doubling of carbon dioxide would produce is lower, so too is the transient climate response, which the researchers estimate to be about 1.4°C, ranging between 0.8° and 2.2°C.

  Other researchers, however, come to more worrisome conclusions about how sensitive the climate is. Two new studies, one in March and another in May 2014, argue that the many researchers who have reported lower climate sensitivities have failed to take the cooling effects of various pollutants into account. Once the dampening of airborne particles like sulfates and black soot and ground-level ozone is properly included in calculations, the March Nature Climate Change study by GISS researcher Drew Shindell calculated a transient climate response of about 1.7°C. Building on Shindell’s insights, researchers at Texas A&M University estimated in May 2014 that climate sensitivity is likely to be 3.0°C, ranging between 1.9° and 6.8°C. This range is a bit higher and wider than the one reported by the IPCC in 2013. However, more recent research cited earlier that now finds that man-made aerosols have had a negligible effect on current global average temperatures might suggest that these climate sensitivity ranges are too high.

  In September 2014 the climate sensitivity research pendulum swung back toward a lower estimate. In their article published in Climate Dynamics, Georgia Tech climatologist Judith Curry and British statistician Nicholas Lewis reported results using temperature data from 1850 to 2011 along with estimates of the effects on climate of various factors taken from the IPCC’s Fifth Assessment Report, such as land-use changes, volcanic activity, and atmospheric pollutants. They calculate that the best estimate for climate sensitivity is 1.64°C, with an uncertainty range of 1.05° to 4.05°C. The corresponding transient climate response is 1.33°C, with an uncertainty range of 0.90° to 2.50°C. These new values are at the low end of the IPCC climate sensitivity and transient climate response estimates.

  Is there any way to resolve this scientific dispute? Yes. Wait and see what the climate actually does. But climatologists may have to wait at least a couple of decades before they can know the answer for sure. In an April 16, 2014, article in Geophysical Research Letters, researchers sort through various climate sensitivity scenarios ranging from a low of 1.5° to a high of 6.0°C. They calculate that it would take another twenty years of temperature observations for us to be confident that climate sensitivity is on the low end and more than fifty years of data to confirm the high end of the projections. This ongoing controversy is important because lower climate sensitivity would mean that future warming will be slower, giving humanity more time to adapt and to decarbonize its energy production technologies. Higher climate sensitivity would mean the opposite.

  Ocean Acidification

  As the oceans absorb carbon dioxide from the atmosphere, the amount of carbonic acid is increased, thus making the ocean more acidic. As noted previously, the acidity of the surface waters of the oceans has increased by about 26 percent since the beginning of the Industrial Revolution. The IPCC 2014 Adaptation report observes, “Impacts of ocean acidification range from changes in organismal physiology and behavior to population dynamics and will affect marine ecosystems for centuries if emissions continue.” Some ocean denizens like plants and algae will most likely benefit from increased carbon dioxide levels, whereas other creatures such as corals and mollusks might suffer significant harm. Corals, echinoderms, and mollusks absorb carbonate minerals from the oceans to make their shells, and higher acid levels lower dissolved amounts of that mineral in seawater. Various computer model projections suggest that as acidity increases, it will be harder to calcifying creatures to survive. However, the 2014 Adaptation report observes, “Limits to adaptive capacity exist but remain largely unexplored.”

  Some researchers are worried that calcifiers like corals might reach a tipping point at which they “collapse.” More recent experimental research on eight species of Pacific reef calcifiers has been a bit more reassuring. Biologists from California State University at Northridge report, “In contrast to previous studies that have predicted rapid decreases in calcification of corals and coral reefs exposed to [more than doubled carbon dioxide], our study, performed at the organismic level on eight of the main calcifiers in Moorea, suggests that tropical reefs might not be affected by OA [ocean acidification] as strongly or as rapidly as previously supposed.” They found that overall reef calcification declined by about 10 percent when carbon dioxide was doubled. In addition, while calcification rates declined with higher and higher levels of carbon dioxide, even when carbon dioxide reached ten times its preindustrial levels, the researchers could identify no tipping points beyond which calcification collapsed. Studies on cold-water Mediterranean corals similarly found that their rates of calcification remained constant even when exposed to levels of carbon dioxide in high-end projections for the end of this century. Nevertheless, published reviews of research on the effects of ocean acidification resulting from high levels of extra carbon dioxide find the overall effects on marine organisms are negative. Of course, if emissions are cut to keep future temperature increases down, that would also limit the effects of ocean acidification.

  How Much Will Global Warming Cost?

  Assume global warming. There are two ways to address concerns about warming: adaptation and mitigation. In 2014, the IPCC issued two reports dealing with both sorts of responses. Climate Change 2014: Impacts, Adaptation, and Vulnerability (hereafter the Adaptation report) describes adaptation as the “process of adjustment to actual or expected climate and its effects.” Climate Change 2014: Mitigation (hereafter the Mitigation report) defines mitigation as “a human intervention to reduce the sources or enhance the sinks of greenhouse gases.” Mitigation basically means cutting the emissions of greenhouse gases like carbon dioxide and/or figuring out how to suck carbon dioxide out of the atmosphere—for example, planting more forests. In other words, people can take steps to defend themselves against the impacts of man-made climate change and/or reduce impacts by trying to slow or stop man-made climate change. Most climate researchers believe that some additional warming is inevitable, so people will have to engage in both activities.

  The IPCC reports offer cost estimates for both adaptation and mitigation. The 2014 Adaptation report reckons, assuming that the world takes no steps to deal with climate change, that “global annual economic losses for additional temperature increases of around 2°C are between 0.2 and 2.0 percent of income.” The report adds, “Losses are more likely than not to be greater, rather than smaller, than this range.”

  In a 2010 Proceedings of the National Academy of Sciences article, Yale economist William Nordhaus assumed that humanity does nothing to cut greenhouse gas emissions. Nordhaus uses an integrated assessment model that combines the scientific and socioeconomic aspects of climate change to assess policy options for climate change control. His RICE-2010 integrated assessment model found that “of the estimated damages in the uncontrolled (baseline) case, those damages in 2095 are $12 trillion, or 2.8% of global output, for a global temperature increase of 3.4°C above 1900 levels.” Nordhaus’s estimate evidently assumes that the world’s economy will grow at about 2.5 percent annually, reaching a total GDP of roughly $450 trillion in 2095.

  What might the world’s econom
y look like by 2100 if no policies are adopted with the aim of mitigating or adapting to climate change? In 2012, the IPCC asked the economists in the Environment Directorate at the Organisation for Economic Co-operation and Development to peer into the future and devise a plausible set of shared socioeconomic pathways (SSPs) to the year 2100. The OECD economists came up with five baseline scenarios. Let’s take a look at a couple of the scenarios to get some idea of how the world’s economy might evolve over the remainder of this century. The OECD analysis begins in 2010 with a world population of 6.8 billion and a total world gross product of $67 trillion (2005 dollars), yielding a global per capita income just shy of $10,000. For reference the OECD notes that US 2010 per capita income averaged $42,000.

  The SSP2 scenario is described as the “middle of the road” projection in which “trends typical of recent decades continue, with some progress towards achieving development goals, reductions in resource and energy intensity at historic rates, and slowly decreasing fossil fuel dependency.” If economic and demographic history unfolds as that scenario suggests, world population will have peaked at around 9.6 billion in 2065 and fallen to just over 9 billion by 2100. The world’s economy will have grown more than eightfold, from $67 trillion to $577 trillion (2005 dollars). Average income per person globally will have increased from around $10,000 today to $60,000 by 2100. US annual incomes would average just over $100,000.

  In the SSP5 “conventional development” scenario, the world economy grows flat out, which “leads to an energy system dominated by fossil fuels, resulting in high GHG emissions and challenges to mitigation.” Because there is more urbanization and because there are higher levels of education, world population peaks at 8.6 billion in 2055 and will have fallen to 7.4 billion by 2100. The world’s economy will grow fifteenfold to just over $1 quadrillion, and the average person in 2100 will be earning about $138,000 per year. US annual incomes would exceed $187,000 per capita.

  It is of more than passing interest that people living in the warmer world of SSP5 are much better off than people in the cooler SSP2 world. The OECD analysis adds with regard to climate change in this scenario that the much richer and more highly educated people in 2100 will face “lower socio-environmental challenges to adaptation result[ing] from attainment of human development goals, robust economic growth, highly engineered infrastructure with redundancy to minimize disruptions from extreme events, and highly managed ecosystems.” In other words, greater wealth and advanced technologies will significantly enhance the capabilities of people to deal with whatever the deleterious consequences of climate change turn out to be.

  As noted above, the IPCC estimates that failure to adapt to climate change will reduce future incomes by between 0.2 to 2 percent for temperatures exceeding 2°C. Yale’s William Nordhaus is one of the more accomplished researchers in this area, trying to calculate the costs and benefits of climate change. In his 2013 book The Climate Casino: Risk, Uncertainty, and Economics for a Warming World, Nordhaus notes that a survey of studies that try to estimate the aggregated damages that climate change might inflict at 2.5°C warming comes in at an average of about 1.5 percent of global output. The highest climate damage estimate Nordhaus cites is a 5 percent reduction in income. The much criticized 2006 Stern Review: The Economics of Climate Change suggested that the business-as-usual path of economic growth and greenhouse gas emissions could even reduce future incomes by as much as 20 percent.

  Future temperatures will perhaps exceed these, but transient climate response temperatures over the remainder of the century are likely to be close to the 2.5°C benchmark cited by the IPCC. In the scenarios sketched out above, a 2 percent loss of income would mean that the $60,000 and $138,000 per capita income averages would fall to $58,800 and $135,240, respectively. Stern’s more apocalyptic estimate would cut 2100 per capita incomes to $48,000 and $110,400, respectively. How much should people living now on incomes averaging $10,000 per year spend to make sure that people whose incomes will likely be 6 to 14 times higher aren’t reduced by a couple of percentage points? As Nordhaus observes, “Most philosophers and economists hold that rich generations have a lower ethical claim on resources than poorer generations.”

  The Costs and Benefits of Trying to Stop Warming

  Making the heroic set of assumptions that all countries of the world begin mitigation immediately and adopt a single global carbon price, and all key low- and no-carbon technologies are now available, the IPCC’s 2014 Mitigation report estimates that keeping carbon dioxide concentrations below 450 ppm by 2100 would result in “an annualized reduction of consumption growth by 0.04 to 0.14 percentage points over the century relative to annualized consumption growth in the baseline that is between 1.6 percent and 3 percent per year.” The median estimate in reduced annualized growth in consumption is 0.06 percent.

  The IPCC Mitigation report notes that the optimal scenario that it sketches out for keeping greenhouse gas concentrations below 450 ppm would cut future incomes by 2100 by between 3 and 11 percent. How much would that be? As was done with regard to the losses from a lack of adaptation, let’s look at how much the worst-case mitigation scenario might reduce future incomes. Without extra mitigation, the increase of global gross product to $577 trillion in the middle-of-the-road scenario implies an economic growth rate of 2.42 percent between 2010 and 2100. Cutting that growth rate by 0.14 percentage point to 2.28 percent yields an income of $510 trillion in 2100, reducing per capita incomes from $60,000 to $57,000 per capita. Growth in the conventional-development scenario is cut from an implied 3.07 percent to 2.93 percent, reducing overall income from over $1.015 quadrillion to $901 trillion and cutting average incomes from $138,000 to $122,000.

  All of these figures must be taken with a vat of salt since they are projections for economic, demographic, and biophysical events nearly a century from now. That being acknowledged, projected IPCC income losses that would result from doing nothing to adapt to climate change appear to be roughly comparable to the losses in income that would occur following efforts to slow climate change. In other words, it appears that doing nothing about climate change now will cost future generations about the same as doing something now.

  Climate Change Is Not Increasing Damage—Yet

  People concerned about catastrophic man-made climate change have been seeking evidence that it is boosting risks now among the weather damage and loss data. “This is climate change. We were warned about extreme weather. Not just hot weather, but extreme weather,” Senator Barbara Boxer (D-CA) declared on the floor of the US Senate in May 2013 in response to the tornado that devastated Moore, Oklahoma. “You’re going to have tornadoes and all the rest.” The activists over at Greenpeace did not put too fine a point on the destruction caused by Superstorm Sandy hitting New York and New Jersey in the fall of 2013: “Hurricane Sandy = Climate Change.” One problem: Researchers can find no such trends with respect to the damage caused by tornadoes and hurricanes.

  The 2012 United Nations’ Special Report for Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) projects man-made global warming will boost the damage caused by heat waves, coastal floods, and droughts as they get worse by the end of the century. The researchers, however, could not draw firm conclusions about the effects of climate change on any current trends in hurricanes, typhoons, hailstorms, or tornadoes. The IPCC’s Climate Change 2014: Synthesis Report noted that there is low confidence that climate change has so far affected any global trends toward increased flooding, hurricanes and typhoons, or droughts. That report did note that “increasing exposure of people and economic assets has been the major cause of long-term increases in economic losses from weather- and climate-related disasters.” In other words, the weather is not necessarily getting worse; there are simply more people and property for storms to damage.

  The SREX study expressed medium confidence that droughts had increased in some areas as a result of man-made climate change. An authoritative November
2012 article in Nature later found that the previously reported increase in global drought is overestimated because the widely used Palmer Drought Severity Index doesn’t, among other issues, properly account for evaporation rates. Consequently, based on more realistic calculations that take into account changes in available energy, humidity and wind speed, the researchers concluded that “there has been little change in drought over the past 60 years.” The 2013 IPCC Physical Science report essentially concurred, observing that there was “low confidence in detection and attribution of changes in drought over global land areas.” (In December 2014, NOAA issued a study that concluded that man-made climate change was not a factor in the extreme drought that has beset California since 2011.)

  The 2012 SREX report acknowledges, “In many regions, the main drivers for future increases in economic losses due to some climate extremes will be socioeconomic in nature.” In other words, any surge in weather disaster damage is largely due to an increase in what can potentially be destroyed and the number of people exposed to it.

  Can researchers now discern any effect that the recent increase in global average temperature has had on people and their property? Not really.

  For example, a 2011 report by the libertarian Reason Foundation, Wealth and Safety: The Amazing Decline in Deaths from Extreme Weather in an Era of Global Warming, 1900–2010, notes, “Aggregate mortality attributed to all extreme weather events globally has declined by more than 90 percent since the 1920s, in spite of a four-fold rise in population and much more complete reporting of such events.” The death rate from droughts is 99.9 percent lower than it was in the 1920s; the death rate from floods is 98 percent lower; and the death rate from big storms like hurricanes has declined more than 55 percent since the 1970s.