Greenhouse gases are on track to soar far beyond levels scientists warn will trigger some of the most dangerous effects of global warming, according to a major United Nations' climate-panel study released Sunday.
The Intergovernmental Panel on Climate Change report lays out a harsh challenge for the world: To have a "likely" shot at limiting the planet's temperature rise to 2 degrees Celsius (3.6 degrees Fahrenheit) above preindustrial levels, the world must cut its greenhouse-gas emissions by 40 percent to 70 percent by 2050 compared with 2010 levels — and must get emissions to near-zero levels by 2100.
Here are six more key takeaways from the sweeping report on battling climate change.
We're Still Doing It Wrong, Even if We're Trying Harder: Nations worldwide are increasingly taking steps to stem emissions. "In 2012, 67% of global GHG emissions were subject to national legislation or strategies versus 45% in 2007," the report states. Lots of those efforts are in their early stages, so it's tough to say what their overall effect will be.
But what's clear right now is that emissions are still rising, along with efforts to rein them in. Global emissions grew faster between 2000 and 2010 than they did during the 1970-2000 period, the report states.
Time Is Running Out: "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 relative to preindustrial levels," the report states.
German economist Ottmar Edenhofer, who cochaired the IPCC panel that produced the study, noted that while "substantial" investment is needed globally, "avoiding further delays in mitigation and making use of a broad variety of technologies can limit the associated costs."
Slashing Emissions Won't Throttle the Economy: The good news, the IPCC concludes, is that much wider adoption of carbon-cutting technologies is possible without slamming the brakes on economic growth.
The IPCC believes that stabilizing atmospheric carbon dioxide at a level consistent with the 2-degree target would trim growth by a median estimate of just 0.06 percent annually this century, a small fraction of a "baseline" growth forecast of 1.6 to 3 percent per year.
And that tally doesn't even include economic benefits of tempering dangerous global warming, which is creating an array of harms and risks for human health, ecosystems, food production in some areas, and more.
Renewables Have Arrived, But Still Need Help: The IPCC says that in the majority of pathways to stabilize emissions for a 2-degree rise, low-carbon sources such as renewables, nuclear, and carbon capture for fossil-fuel power plants must rise from their current share of 30 percent globally to 80 percent at mid-century.
The authors note that since their last big report in 2007, renewables have gotten cheaper and perform better, but still need "direct and/or indirect support" to significantly expand their market share.
A related point: The authors endorse removing subsidies for fossil fuels as a way to help stem emissions. It's easier said than done, though. The International Energy Agency last year said subsidies rose to $544 billion worldwide in 2012, despite reform efforts.
Cities Are Very Important and a Little Tricky: The number of people living in cities worldwide is soaring; in 2011 a little over half of the world's population lived in urban areas, and by 2050 that's expected to reach as high as 69 percent, the report notes. This provides a "window of opportunity" to implement the right mix of policies, and those policies will work best when "bundled."
"Effective mitigation strategies involve packages of mutually reinforcing policies, including co"locating high-residential with high-employment densities, achieving high diversity and integration of land uses, increasing accessibility, and investing in public transport and other demand-management measures," the report states.
Natural Gas, Done Right, Is an Ally in the Climate Fight ... for Now: The report gives a nod to natural gas. The world could improve its carbon count by moving away from coal plants to the most modern, high-efficiency natural-gas plants — provided that the greenhouse-gas leaks associated with drilling natural gas are minimized.
"GHG emissions from energy supply can be reduced significantly by replacing current world average coal"fired power plants with modern, highly efficient natural-gas combined"cycle power plants or combined heat and power plants, provided that natural gas is available and the fugitive emissions associated with extraction and supply are low or mitigated," the report states.
That may not sit well with swaths of the environmental movement, where support for natural gas is on the wane. But the reports' authors endorse the idea of gas plants, despite their emissions, as a "bridge" technology until nonpolluting sources such as renewables and fossil-fuel plants that trap carbon emissions are the dominant energy supplies.