From one of two excellent 2016 papers by Dr. James E. Hansen et. al. Dr. Hansen was the top American climate scientist at NASA Goddard Institute for Space Studies: NASA GISS until his retirement in April 2013 after 46 years of government service. Many of his works are available to the public at http://www.columbia.edu/~jeh1/
These excerpts are from Dr. Hansen’s first 2016 paper, “Regional climate change and national responsibilities,” with Dr. Makiko Sato coauthoring. It was published 2 March 2016 in Environmental Research Letters, Volume 11, Number 3, http://iopscience.iop.org/article/10.1088/1748-9326/11/3/034009 last retrieved 6/20/2017. The headings are my own additions.
UNDERSTANDING CLIMATE SHIFTS:
Climate as bell curves show decadal shifts toward hot and chaotic
The bell curve shifts in 2005–2015 are only about one-third of the shift that will occur with 2 °C global warming. (Although warming of land areas in 2005–2015 is ~0.8 °C, figure 4, global mean warming is only ~0.6 °C relative to 1951–80; 1951–80 is ~0.3 °C warmer than pre-industrial, Hansen et al (2010), so 2 °C warming above pre-industrial implies 1.7 °C relative to 1951–1980.) Given the approximate linearity between mean temperature increase and bell curve shift, 2 °C global warming would yield a shift of about six standard deviations during summer in the Mediterranean, Middle East, Sahara and Sahel regions and a similar shift in all seasons in the African Rainforest and Southeast Asia (figure 3).
Regional climate decadal shifts as bell curves worse for some
Implications of these regional climate shifts are manifold. We note several consequences, focusing on their geographically uneven impact, especially the difference between developing countries at low latitudes and more developed northern nations. The examples and not a review of these burgeoning research areas, but they are sufficient to introduce discussion of relevance of these regional changes to the issue of dangerous human-made climate change.
UNDERSTANDING CLIMATE CHANGE CONSEQUENCES:
Climate change and human conflict
Hsiang et al (2013) assemble the results of 60 quantitative studies of the relation between climate change and human conflict spanning the last 10 000 years and all major world regions. They find that interpersonal violence increases by 4% and intergroup conflict by 14% for each standard deviation change in temperature toward warmer temperatures. [Standard deviations are the numbers along the bottom axis in the bell curve charts.] Such findings do not constitute natural laws, but they provide a useful empirical estimate of impacts that can be used for at least a limited range of temperature increase. Increases we infer of 2–6 standard deviations with 2 °C global warming imply significant effects in all regions, but with larger effects at lower latitudes. Conflicts in turn tend to result in migrations with effects on both displaced and host populations (McMichael et al 2012).
Climate change and newly uninhabitable areas
Temperature rise itself imposes a strong disproportionately large effect on low latitude countries. Pal and Eltahir (2016) note that business-as-usual fossil fuel emissions result in some regions in the Middle East becoming practically uninhabitable by the end of this century as the wet bulb temperature approaches the level at which the human body is unable to cool itself under even well-ventilated outdoor conditions (Sherwood and Huber 2010) [“fit people can just disintegrate into a pool of useless people on stretchers. That’s what I see happening to society, to cultures” – Huber from “Limits to Adaptability”]. Today’s global temperature distribution has notable nonlinear effect on economic productivity (Burke et al 2015). Middle latitude countries have near-optimum temperature and limited impact from projected temperature change, but, in contrast, warmer countries, such as Indonesia, India and Nigeria are on a steep slope with rapidly declining productivity as temperature rises (figure 2, Burke et al 2015).
Climate change and sea level rise
These regional consequences of warming are accompanied by a threat that sea level rise poses to global coastlines, thus jointly creating a need for prompt strong actions to avoid tragic results. Earth’s history suggests that warming of even 1 °C above pre-industrial levels could eventually lead to 6–9 m sea level rise (Dutton et al 2015). IPCC (2013) estimates that about 1 m or less sea level rise would occur by 2100, but Hansen et al (2015) argue that amplifying feedbacks make a highly nonlinear response likely with potential for several meters of sea level rise this century and recent ice sheet models explore mechanisms that may contribute to rapid ice sheet collapse (Pollard et al 2015). If the ocean continues to accumulate heat and increase melting of marine-terminating ice shelves of Antarctica and Greenland, a point may be reached at which it is impossible to avoid large scale ice sheet disintegration. Given that a majority of large global cities are located on coastlines, sea level rise would add another source of migration pressure.
UNDERSTANDING WHAT MUST BE DONE:
Climate change prevention remains the goal
The United Nations 1992 Framework Convention on Climate Change (UNFCCC 1992) stated its objective as ‘…stabilization of GHG concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system’. The 15th Conference of the Parties (Copenhagen Accord 2009) changed the focus to a goal to ‘…reduce global emissions so as to hold the increase of global temperature below 2 °C…’, and the 21st Conference of the parties added an aspirational goal of below 1.5 °C (Davenport 2015). However, we suggest that the UNFCCC (1992) objective to stabilize GHG concentrations is fundamental and starkly informs policy requirements.
Prompt restoration of 350 ppm CO2 ceiling hard but necessary
Atmospheric CO2 amount, in particular, is a great challenge in limiting GHG concentration. Earth’s paleoclimate history, especially the sensitivity of sea level to global temperature (Dutton et al 2015), and knowledge of Earth’s carbon cycle (Archer 2005, IPCC 2013, ch 6 ) provide a strong constraint, which Hansen et al (2008) use to infer that CO2 must be restored to a level no higher than ~350 ppm, with restoration prompt enough to avoid practically irreversible ocean warming and ice sheet disintegration. This estimate for the CO2 ceiling was affirmed by accurate measurements of Earth’s present energy imbalance (Hansen et al 2011, von Schuckmann et al 2016).
Dangerous human interference with climate system includes both insufficient action and geoengineering
Restoration of CO2 to a level at or below 350 ppm within a century, even with optimistic assumptions about restoration of biospheric and soil carbon, would require reductions of fossil fuel emissions by 5%–7% per year if reductions are started promptly (Hansen et al 2013b). Failure to achieve such reduction will result in continued long-term energy imbalance with Earth’s surface and ocean continuing to warm, growing regional climate impacts, accelerating ice sheet disintegration, and more rapidly rising sea level. As evidence of the situation and consequences grows, there may be increasing calls for climate ‘geo-engineering’ (Royal Society 2009) with unknown consequences (Sillmann et al 2015).
Voluntary goal effectiveness will require a rising price on carbon distributed uniformly to the public
Country-by-country goals, the approach of the 21st Conference of the Parties (Davenport 2015), will not lead to planetary energy balance and climate stabilitzation if fossil fuels are the cheapest energy. It is necessary to include ‘external’ costs to society in the fossil fuel price, especially the costs of climate change and air and water pollution (Ackerman and Stanton 2012), so that carbon-free energies and energy efficiency can supplant fossil fuels more rapidly. Such inclusive pricing of fossil fuels makes economies more efficient and reduces net economic hardships, if the carbon fee, collected from fossil fuel companies at domestic mines and ports of entry, rises gradually and if the funds are distributed uniformly to the public (Hansen 2015).
A few cooperating major powers can and must initiate
A carbon fee can be initiated by a few major economic powers and spread to most nations via border duties on fossil-fuel-derived products from non-participating nations and fee rebates to domestic manufacturers for goods shipped to non-participating nations (Hsu 2011). Issues raised by ‘coercive cooperation’ implicit in border adjustments (Bohringer et al 2012) will be subdued, once the severity and urgency of the climate threat is widely appreciated, by realization that fossil fuels cannot be phased out if some countries are allowed to export products made with untaxed fossil fuels. Developing countries have rights, recognized in the concept of common but differentiated responsibilities, and leverage to achieve economic assistance, which should be tied to the improved agricultural and forestry practices needed to limit trace gas emissions and store more carbon in the soil and biosphere. Finally, international cooperation in generating more affordable carbon-free energies is needed, or economic development in many nations will continue to be based on fossil fuels, despite pollution and climate impacts.
Dr. Hansen is one of my all-time heroes working on behalf of all children to come. DO GET INVOLVED in preserving a livable world: volunteer today –