Large-scale transformations of energy production, land use and lifestyle are required to reduce the greenhouse gas emissions causing global warming, according to the UN’s Intergovernmental Panel on Climate Change (IPCC).
A summary of the latest volume of its Fifth Assessment Report, released yesterday in Berlin, warned current pledges to cut emissions are “not consistent” with the globally-agreed target of capping the rise in temperatures at 2 degrees.
The IPCC noted emissions were now “the highest in human history” and grew by 2.2 per cent annually between 2000 and 2010 compared to 1.3 per cent on average over the previous three decades.
About half of cumulative carbon dioxide (CO2) emissions since the Industrial Revolution “have occurred in the last 40 years”, with burning fossil fuels accounting for 76 per cent of the total in 2010 – followed by methane, nitrous oxide and fluorinated gases.
“Globally, economic and population growth continue to be the most important drivers of increases in CO2 emissions from fossil fuel combustion,” the IPCC said, adding that “the contribution of economic growth has risen sharply” between 2000 and 2010.
“Without additional efforts to reduce greenhouse emissions beyond those in place today, emissions growth is expected to persist [and] result in global mean surface temperature increases in 2100 from 3.7 to 4.8 degrees Celsius compared to pre-industrial levels.”
Scenarios consistent with keeping temperature change below 2 degrees include “substantial cuts” in emissions by 2050 through “large-scale changes in energy systems and potentially land use” – such as higher-density cities.
By 2050, there would have to be more rapid improvements in energy efficiency, a tripling or even quadrupling of the share of zero- and low-carbon energy supply from renewables, nuclear energy, bioenergy and coal burning with carbon capture and storage.
“Delaying mitigation efforts beyond those in place today through 2030 is estimated to substantially increase the difficulty of the transition to low longer-term emissions levels and narrow the range of options consistent with maintaining temperature change below 2 °C.”
The summary noted estimates of the economic costs of mitigation “vary widely”, but were likely to amount to 0.6 per cent of global GDP. Its own cost-effective benchmark scenario assumed a single global carbon price and the availability of all key technologies.
However, it warned that infrastructure developments and spatial planning that locked societies into high emissions “may be difficult or very costly to change” due to the long lifespan of buildings.
It suggested emissions could be substantially reduced through changes in consumption patterns – changing the ways we travel, using less energy and longer-lasting products in households as well as dietary change and less food waste.
Decarbonising electricity generation is seen as a key component of cost-effective mitigation. This could involve increasing the share of renewables (such as wind and solar) and nuclear energy from 30 per cent currently to 80 per cent by 2050.
The IPCC acknowledged nuclear energy faced “barriers”, including operational risks, uranium mining risks, regulatory risks, unresolved waste-management issues, nuclear weapon proliferation concerns and adverse public opinion.
With transport accounting for 27 per cent of final energy use in 2010 and its emissions projected to double under “business-as-usual”, it said this could be offset by fuel efficiency improvements, behavioural change and better policy implementation.
However, the report also said transport emissions could be reduced by up to 40 per cent by 2050 with “technical and behavioural mitigation measures for all transport modes”, including higher vehicle efficiency, as well as new infrastructure and urban redevelopment.
“Integrated urban planning, transit-oriented development, more compact urban form that supports cycling and walking can all lead to modal shifts as can, in the longer term . . . high-speed rail systems that reduce short-haul air travel demand.
On buildings, which account for about 32 per cent of final energy use, the report warned that emissions could increase by up to 150 per cent by 2050 due to more wealth, lifestyle change, access to modern energy services and adequate housing, and urbanisation.
“For new buildings, the adoption of very low energy building codes is important and has progressed substantially,” it said. “In countries with established building stocks, reductions of heating/cooling energy use by 50-90 per cent in individual buildings have been achieved.”
On industry, which accounts for just over 30 per cent of global emissions, the IPCC said the sector’s energy intensity could be “directly reduced by about 25 per cent” through upgrading, replacement and deployment of best technologies. Referring to agriculture, the report blamed most of the emissions on deforestation, soil and nutrient management, and livestock. However these are projected to decline by 2050 due to afforestation, better cropland management and the “restoration of organic soils”.
