Wednesday, April 17, 2013

Worsening planetary energy imbalance and climate change

The existence of anthropogenic climate change has firm scientific evidence, no matter what global warming denialists say with no evidence or with interests (Hansen, Sato, & Ruedy, 2012; Washington & Cook, 2011). Although many ill-informed politicians, self-interested organizations, and even some scientists in non-atmospheric circles tried to discredit science of climate change (Nordhaus, 2012), global warming represented by a figure called “hockey stick” is undeniable (Mann, 2012).

Recent estimates of Earth’s energy budget clearly indicate that anthropogenic global warming is happening at annual net energy gain rates of 0.6±0.4 W/m2 (i.e., 0.6 = 340.2 (incoming solar) − 239.7 (outgoing longwave radiation) − 99.9 (reflected solar) W/m2) over 2000-2010 (Stephens et al., 2012). To be more specific, the net energy imbalance was annually 0.9 ± 0.5 W/m2 over 2000-2005 (Trenberth & Fasullo, 2012) and 0.58 ± 0.15 W/m2 over 2005-2010 (Hansen, Sato, Kharecha, & von Schuckmann, 2011). This energy imbalance is mainly caused by burning fossil fuels (Dukes, 2003), the vast majority of which had been stored underground for millions of years before the Industrial Revolution began to utilize coal steam engines from around 1760. Instead of searching for alternative and more sustainable energy sources, globalized energy industry is “ripping apart the earth” to extract more fossil fuels (McKibben, 2012).

Because the environment is “warmer and moister than it used to be” (Trenberth, 2012, p. 7), all weather events as well as extreme ones are affected by the current climate change. Hurricane Katrina in August 2005 (Graumann et al., 2006) was a dramatic symbol of how human inaction will worsen the climate change and harm humans themselves (Karl, Melillo, & Peterson, 2009; Lynn, Healy, & Druyan, 2009). Hurricane Sandy in October 2012 wreaked more havoc on lower Manhattan in New York and shorelines in New Jersey by exacerbated storm surge due to sea-level rise, which is undeniably caused by human induced global warming (Gillis, 2012).

Therefore, sustainability cannot be achieved without climate change mitigation. One of the most evident ways to minimize the adverse effects of human activities is to minimize greenhouse emissions, as suggested by the Intergovernmental Panel on Climate Change (IPCC) (Core Writing Team, Pachauri, & Reisinger, 2007). The more we delay to reduce greenhouse gas emissions drastically, the harder it becomes that we contain global warming within manageable limits. However, time is running out (Ranger et al., 2012; van Vliet et al., 2012). The latest estimation for the global carbon dioxide emissions in 2012 shows a trend worse than the IPCC’s worst warming scenario (Peters et al., 2012).

Although some recent studies indicate that imminent peak production of fossil fuels will eventually limit global CO2 emissions (Rutledge, 2011; Vernon, Thompson, & Cornell, 2011), even their analyses can be counter-argued by scientists’ analyses showing even fossil fuel reserves that are significantly lower than IPCC scenarios can induce catastrophic climate changes (for example, Kharecha & Hansen (2008)). We have to prepare for worst cases by reducing emissions right now (Oreskes, Stainforth, & Smith, 2010).

Then what should be our goal for climate change mitigation? It is widely accepted that we have to confine global warming within 2 °C above the pre-industrial global average temperature (Knopf, Kowarsch, Flachsland, & Edenhofer, 2012; UNEP, 2010; UNFCCC, 2010). According to the IPCC’s new climate change scenario called Representative Concentration Pathways (Moss et al., 2008), the organization’s targets in 2100 to limit global surface temperature change within 2 °C since industrialization is 2.6 W/m2 of radiative forcing increase since industrialization and the CO2 equivalent concentration of greenhouse gas should be limited to 450 ppm (van Vuuren et al., 2012). By definition, all values for the pre-industrial era should be based on those of the year 1750 (Core Writing Team et al., 2007, p. 36). However, climate models of the IPCC run their simulations by setting the benchmark year as any year between 1765 and 1850, for there are not a significant change in greenhouse gas concentrations during the period (Meinshausen et al., 2011).

How much is the amount of greenhouse gas emissions that are equivalent of the warming limit? It is recently estimated that we have to reduce our CO2 emissions by more than 80% compared to a peak emissions to stabilize a CO2 concentration at any chosen target level within a century or so (Committee on Stabilization Targets for Atmospheric Greenhouse Gas Concentrations, 2011).

Then what are we humans doing to achieve the target? Sadly, we are not doing enough, if not nothing. Although the Kyoto Protocol and its child EU ETS have given us a small bit of hope, the skepticism of environmentalists and scientists against any kind of selfless negotiations between nations turned out to be right. Copenhagen Climate Change Conference (COP15/CMP5) held in 2009 didn't produce any tangible, legally-binding agreement between nations. Its outcome, the Copenhagen Accord, just voiced the world’s agreed concern that global average temperature 2 °C warmer than pre-industrial age was unacceptable (UNFCCC, 2010).

The outcome of Durban Climate Change Conference (COP17/CMP7) held in 2011 was creation of an “Ad Hoc Working Group on the Durban Platform for Enhanced Action” (“Durban Platform”). COP17 just promised that the Durban Platform will prepare a legally binding protocol ratified by countries no later than 2015. But this time, global leaders admitted that holding global average temperature increase below 2 °C above pre-industrial levels might not be sufficient to avoid anthropogenic catastrophe and began to mention 1.5 °C (UNFCCC, 2012).

Today, I don’t have an answer about what we have to do for real outcome for global climate change mitigation. In my future post, I’ll search for promising answers.


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