The world is on track for dangerous climate change, having nearly lost room for further pollution in the mix of gases that make up the atmosphere. Despite a rise in clean, renewable energy supplies in certain countries, and a partial shift from coal to natural gas in others, global greenhouse gas pollution continues to rise—and at an increasing pace in the most recent years.
"Economic and population growth are drivers for emissions and they have outpaced the improvements of energy efficiency," said Ottmar Edenhofer, economist at the Potsdam Institute for Climate Impact Research in Germany and co-chair of Working Group III of the Intergovernmental Panel on Climate Change (IPCC). Edenhofer spoke at an April 13 press conference in Berlin, where IPCC's Working Group III released its report on the subject of how to mitigate the climate problem.
Nations worldwide have to make major change in energy supply, soon, if they are to restrain climate change to no more than 2 degrees Celsius, Edenhofer and others said. That is a threshhold beyond which serious harm is likely to occur to human civilization as well as the natural world, by the IPCC and other's scientific judgment.
Geoengineering will probably also be required to solve the planet’s global warming pollution problem, Edenhofer and the report noted. The world will also need a crash course in technologies to capture carbon dioxide—the primary greenhouse gas— from the atmosphere to restrain global warming. Without such CCS hopes of restraining climate change to no more than 2 degrees C warming are "no longer feasible," Edenhofer argued. "In the end, two degrees means the phase out of fossil fuels without CCS entirely in the next few decades."
Energy mix
Climate change is an energy problem. Burning fossil fuels to produce electricity or heat is responsible for roughly half of global warming pollution. Tacking on industry in general, including producing cement, steel, plastics and chemicals, accounts for 78 percent of greenhouse gases, which invisibly accumulate in the atmosphere and trap extra heat.  Such climate changing pollution continues to increase—in 2010, the world emitted some 49 billion metric tons of greenhouse gases, thanks largely to increased coal burning in countries such as China. The number has continued to increase in recent years. In fact, human society added half of the global warming pollution that is in the atmosphere in just the last 40 years.
Restraining global warming to no more than 2 degrees Celsius will require changing how the world produces and uses energy to power its cities and factories, heats and cools buildings, as well as moves people and goods in airplanes, trains, cars, ships and trucks, according to the IPCC. Changes are required not just in technology, but also in people's behavior. "We can reduce through substantial behavioral change and lifestyle change the demand for energy and the consumption of energy," noted Ramon Pichs-Madruga, economist at Cuba's Center for the Investigation of the Global Economy and co-chair of the Working Group III report. And that change "allows for greater flexibility when we come to [choose] technology options. If we leave it all up to technology the costs and risks will be much greater."
The initial IPCC report in this series, released last September, noted that the atmosphere could bear only 800 to 1,000 billion metric tons of greenhouse gases, in order to restrain global warming to 2 degrees Celsius by century's end. The world has already emitted in total roughly 515 billion metric tons. At present rates of pollution then, human society would blow through its carbon budget in the next decade or so.
Such pollution has already doubled just since 1970 and the rates of pollution have been increasing by roughly 1 billion metric tons per year in recent years, a pace that must slow and stop soon. To hold global warming in check requires reducing current emission levels by as much as 70 percent by 2050, compared with 2010 levels, and nearly eliminating such pollution by 2100. Instead, "over the last decade, we have seen increasing use of coal," the fossil fuel that when burned results in the most CO2, Edenhofer noted.
That pace of pollution now needs to slow and then reverse, likely requiring technologies that could pull CO2, the primary greenhouse gas, back out of the atmosphere. Such geoengineering could include technologies ranging from burning trees or grasses and capturing and storing the resulting CO2 from smokestacks to artificial trees that suck CO2 out of the sky directly for storage or re-use. "This group of technologies is essential for low stabilization targets," Edenhofer said.
The problem is that none of this technology exists or, where it does as in the case of CCS, has not been deployed at a large enough scale, because it costs much more than the alternative: freely polluting the atmosphere. More aggressive geoengineering techniques—blocking sunlight and the like—remain too uncertain and fraught with risks to properly evaluate, this IPCC panel argued.
At the same time, emissions from traditional energy supplies must be zeroed out, either through CCS or replacement with less polluting energy sources, whether emissions-free wind and sun or lower carbon nuclear energy. Most of that change will have to take place in the developing world, whether replacing China's new coal-fired power plants or building wind, solar or geothermal facilities to power development in African countries. Fracking to free more natural gas from shale can help displace even more polluting coal in more developed countries such as the U.S. but can only serve as a bridge—and a very short bridge—to the zero-greenhouse-gas pollution future, unless also outfitted with carbon capture and storage to eliminate pollution. Fortunately, scientific surveys indicate that there is enough below-ground storage capacity in the Earth to accommodate humanity's swelling CO2 pollution.
Social change
All of this will also require a major change in investment, reducing money that continues to pour in to dig up fossil fuels by 20 percent per year (thus devaluing those deposits as well) and growing investment in, say, renewables by 100 percent per year. The cost of this transformation is not entirely clear. The IPCC suggests that the median estimate of paying for the change would take off 0.06 percent from global economic growth per year, a small part of a predicted minimum 1.6 percent annual growth globally, but still a restraint. "It's a delay of economic growth but it is not sacrificing economic growth," Edenhofer noted, adding that this calculation does not take into account related benefits, such as a reduction in deadly air pollution and saved human lives, or salvaged nature. "It does not cost the world to save the planet."
Long-term climate stability would require "unprecedented" global cooperation, with countries agreeing to a plan that would set a global price on such pollution. As it stands, the countries of the United Nations Framework Convention on Climate Change have agreed to draft a global treaty by 2015, which would take effect in 2020. At the same time, the 1.3 billion people without access to electricity and the 3 billion or so who still rely on burning wood or dung to fuel cooking or heating would need modern energy supplies, although this might prove to have minimal impacts on climate change through saving forests and other side effects.
Without any action, the world is on track to achieve at least 4 degrees C warming of global average temperatures by 2100, as the world hits 450 parts-per-million of greenhouse gases in 2030 and goes on to put out enough greenhouse gas pollution to achieve as much as 1300 ppm by 2100. Even restraining warming to just 3 degrees C would require substantial transformation. "What has to be done over the next 20 to 30 years or so does not change even if one relaxes the temperature target," Edenhofer said. "Irrespective of the long-term mitigation goal, we have to start to bring the mitigation train onto the track."
The IPCC suggests that atmospheric concentrations of greenhouse gases should not exceed 450 ppm to meet nations' expressed aspiration to hold temperature rise to 2 degrees C or less. Already, atmospheric concentrations of just CO2 have reached 400 ppm at times and all greenhouse gases put together are now at 430 ppm. As a result, global average temperatures have already increased by 0.85 degree C. "If we really want to bring about a limit of the temperature increase to no more than two degrees," said IPCC chair Rajendra Pachauri, "the high-speed mitigation train would need to leave the station very soon and all of global society would need to get on board."
The tracks that train would run on remain mostly unlaid and the exact route on the IPCC's map as presented here is not entirely clear. The route must go through the world's swelling cities, which provide the biggest opportunity to lock in pollution reductions, and the direction and speed—greenhouse gas pollution going down soon and fast—are apparent. This report "provides hope, modest hope," Edenhofer said. "We have the means to do this but it remains a huge, huge challenge."