COP21: Can we avoid climate apocalypse?

Updated 5:40 AM EST, Mon November 30, 2015

Story highlights

World leaders meet in Paris on November 30 at the COP21 climate summit

CNN Opinion invited experts to share their views on what the best solutions are

(CNN) —  

It’s probably the most important number you’ve never heard of: 2 degrees Celsius.

That’s when climate change starts to get especially dangerous. Nearly every country in the world has agreed that 2 degrees of warming, measured as an increase in global average temperature since the Industrial Revolution, is too much to tolerate. Yet there’s less agreement about how to achieve the ambitious goal of keeping the increase below that threshold, and how economies can switch quickly enough from dirty fuels like coal and oil to cleaner sources of energy like solar and wind.

World leaders meet in Paris starting on November 30 to discuss all of this at the COP21 meeting of the UN Framework Convention on Climate Change. We invited authors, experts and activists to weigh in on the 2-degree target. What’s at stake? And how can we actually get there?

Want to tackle the challenge? Tell us how you think climate change will affect your local community, or try seeing how your views affect climate change with this calculator.

Mark Lynas: A catastrophic future

Call it the nightmare scenario. First, world leaders meeting in Paris this December fail to agree on a plan to cut back global greenhouse gas emissions. Renewables like solar power remain too expensive, and people stay irrationally scared of carbon-free nuclear. The world shifts back to burning coal.

Mark Lynas
Courtesy Mark Lynas
Mark Lynas

Then we find out that the Earth’s “climate sensitivity” – how quickly and drastically the planet responds to carbon emissions – is at the upper end of the range scientists predicted. Tipping points are crossed: Methane starts to belch out of the melting permafrost in huge quantities, and the ice sheets respond with what experts euphemistically call “nonlinear disintegration.” Sea levels begin to shoot up.

In the latter part of this century we find the planet’s temperature rise pushing not 2 degrees, as is the current internationally agreed maximum target, but 4, 5, even 6 degrees Celsius of warming. Large areas of the subtropics become biologically uninhabitable to humans: It’s simply too hot to go outside. Food crops in breadbaskets wither in searing heatwaves, and extreme cyclones pummel coastal cities already under threat from the rising seas.

Could human civilization survive? We don’t know – but this nightmare scenario is surely a risk we should not take. We know how to make the shift away from fossil fuels. The time to act is now.

Mark Lynas, a British journalist, is the author of “Six Degrees: Our Future on a Hotter Planet.”

Kathy Kijiner: It should be 1.5 degrees

Scientists have warned that should the world exceed a global temperature increase of 2 degrees, catastrophe of the worst kind will hit. They have stated that 2 degrees is the safe zone.

Kathy Kijiner
Remi Chauvin/Photograph: Remi Chauvin
Kathy Kijiner

However, in these same reports, scientists will add, almost as an afterthought, that at 2 degrees, the Marshall Islands – my home – and all low-lying atolls will be under water.

This is why our island leaders push for 1.5 degrees as the target, instead of 2 degrees. And yet 1.5 degrees continues to be a debate instead of the bottom line. The argument is that 2 degrees is achievable and a more realistic goal. But this comes at the expense of hundreds of atolls and thousands of lives.

If we prioritize 2 degrees as our target for global temperature, we are sentencing atoll nations to death. World leaders must not allow this to happen. I urge the world to hear our people’s pleas and to save our islands.

Kathy Kijiner is a Marshall Islands environmental activist.

Van Jones: Embrace Obama’s ‘Clean Power Plan’

The age of fossil fuels helped America build its industrial might. But it came at a great cost, from children with asthma to global climate disruption.

We must keep global warming below a 2-degree increase or it will put our very society at risk. To get there, we need to stop the nonsense and embrace the future. In the wake of President Obama’s recent decision on the Keystone XL pipeline, a new consensus is emerging that we must keep remaining fossil fuels in the ground.

Van Jones
Van Jones

Obama’s “Clean Power Plan” is a good start, and it needs to be fully implemented. Americans need to take the Clean Power Plan and build on it with strong commitments to powering America with 50% clean energy by 2030. This will put us on a path to powering America with 100% clean energy by 2050 and send a signal to entrepreneurs and other nations.

Unfortunately, Republicans appear to be just as addicted to donations from fossil fuel interests as our nation is addicted to those fossil fuels. They are currently mounting an attack on the Environmental Protection Agency’s common-sense plan to reduce global warming polluting from coal-fired power plants.

But there is hope. In every presidential debate, Republican nominees bemoan the lack of good American manufacturing jobs. At some point, they will catch on to the fact that those jobs exist – in renewables. Today solar and wind employ more Americans than coal.

If we keep the focus on the future and well-paying, 21st-century jobs, we can overcome the fierce opposition of fossil fuel diehards and build a bipartisan consensus. Congress needs to stop burying its head in the tar sands. Our future is not down those holes. Our future is in clean energy and in the hands of the workers, inventors, entrepreneurs, and bold leaders who will lead the way.

Van Jones is president of Dream Corps and Rebuild the Dream, which promote innovative solutions for America’s economy. He was President Barack Obama’s green jobs adviser in 2009. A best-selling author, he is also founder of Green for All, a national organization working to build a green economy. Follow him on Twitter @VanJones68.

Fatih Birol: Is 2 degrees doable?

Since the first Conference of Parties in 1995, global greenhouse gas emissions have risen by more than 25% and the atmospheric concentration of these gases has marched steadily higher. As the largest source of global greenhouse gas emissions, actions in the energy sector can make or break efforts to achieve the world’s agreed climate goal, while sustaining global economic growth and bringing modern energy to the billions who lack it today.

Fatih Birol
Eric Malemanche
Fatih Birol

Is a dramatic transformation of the energy sector possible?

There are encouraging signs that the transition is already underway. Renewables have been gaining momentum – collectively, they accounted for more than 40% of new power generation capacity worldwide in each of the last four years. And energy efficiency efforts have spread: The International Energy Agency’s World Energy Outlook 2015 estimates that the share of worldwide final energy consumption that is covered by energy efficiency regulations reached 27% in 2014, almost twice the level of 2005.

Pledges for Conference of Parties 21 in Paris will have a positive impact, but are consistent with an average global temperature increase of around 2.7 degrees Celsius by 2100, falling short of the global goal of 2 degrees. COP21 must establish a clear long-term vision and certainty of action that will drive the right investments and accelerate the energy sector transition.

Fatih Birol is the executive director of the International Energy Agency.

Bjorn Lomborg: Ineffective responses so far

For 20 years, governments have tried to cut carbon emissions. The result has been two decades of failure with ever-increasing global emissions.

Governments have already revealed the carbon cuts they likely will commit to in Paris. All of these combined will reduce temperatures by a tiny 0.05 degrees Celsius (0.09 degrees Fahrenheit) by 2100. Yet the cost is likely to be more than $1 trillion annually.

Björn Lomborg
Charlotte Carlberg Bärg
Björn Lomborg

Carbon-cutting promises are ineffective and costly because solar and wind are far too expensive and inefficient to replace fossil fuels. We get a minuscule 0.4% of total global energy consumption from solar and wind, according to the International Energy Agency, and even by 2040 that will have reached only 2.2%.

We should end fossil fuel subsidies and invest much more in green energy research and development. This would be much cheaper and more effective than our current approach. We need to innovate the price of green energy down to where everyone wants to buy it. And we should acknowledge that wasting $1 trillion annually on minuscule temperature reductions is immoral and wasteful when there are major needs today – from malaria to nutrition to family planning – where small investments could achieve a great deal more.

Bjorn Lomborg, president of the Copenhagen Consensus Center, is the author of “The Skeptical Environmentalist” (Cambridge Press, 2001) and “Cool It” (Knopf, 2007).

David Keith: Try solar geoengineering

One the most powerful options to counter climate change is solar geoengineering: an engineered increase in the Earth’s reflectivity, resulting in cooler temperatures for the planet’s surface. It might be done by injecting sulfate aerosols or even diamond dust into the stratosphere, where they would reflect sunlight just as do the droplets in a very thin cloud layer.

David Keith
Courtesy David Keith
David Keith

It is not a substitute for cutting emissions – it is a supplement. We can’t keep using the atmosphere as a waste dump for carbon and expect to have good climate, no matter what we do to reflect away some sunlight.

The combination of emissions cuts and solar geoengineering could limit climate risks in ways that simply cannot be achieved by emissions cuts alone. It could, for example, allow the world to stay under the 2-degree mark.

But it makes no sense to start geoengineering today, since the uncertainties are far too large and the world lacks adequate mechanisms for governance.

We need research to sharpen our understanding on how to reduce the risks. Yet the U.S. has no research program on solar geoengineering because of a taboo based on the fear that it will lessen efforts to cut emissions. This is like refusing to develop chemotherapy for lung cancer out of fear that it will encourage smoking.

If we have no research program, then we give our children the gift of ignorance. If climate change is worse that we expect, then they will have to make decisions about geoengineering on that basis.

David Keith is the Gordon McKay professor of applied physics and professor of public policy at Harvard University. He is the author of “A Case for Climate Engineering.”

Nancy Harris: Deforestation has to stop

All life depends on plants. Forests regulate climate and water cycles while providing the food, fiber, fuel, livelihoods and genetic resources upon which human societies depend.

Nancy Harris
Courtesy Nancy Harris
Nancy Harris

In many tropical developing countries, greenhouse gas emission profiles are dominated not by fossil fuels, as for developed countries, but by deforestation. Here, it’s a land management challenge. Every day, nearly 25,000 soccer fields of tropical forests are lost. Brazil’s deforestation rates have dropped 70% since 2004, but loss is accelerating in other countries such as Indonesia, Democratic Republic of the Congo and Madagascar. How can they stop the deforestation that contributes 12% to 15% to human-caused emissions while still achieving their development goals?

It won’t be easy, but Brazil has shown it’s possible. As we wait for improved technologies in the energy and transportation sectors, reducing emissions from deforestation represents a low-cost and immediate option for limiting global warming to 2 degrees.

All countries can participate. Climate change impacts don’t follow national borders, so it’s in our collective interest to support the leadership of tropical countries in their transition away from a dependence on natural resource depletion and toward the preservation of forest landscapes, a critical element of current and future life on earth.

Nancy Harris is research manager of Global Forest Watch at World Resources Institute.

Michael Mann: Aim for renewable energy

We have seen significant commitments from the leading emitters – the U.S., China, and now India – to make substantial reductions in emissions. The collective pledges from all countries going to COP21 are already enough to get us halfway (3.5 degrees Celsius warming) from “business as usual” warming of 5 degrees to 2-degree stabilization. Through hard-nosed negotiations in Paris we ought to be able to get even closer.

Michael Mann
Courtesy Michael Mann
Michael Mann

COP21 isn’t the end-all in the battle to avert dangerous climate change. It’s just the next step in an ongoing process.

In the years ahead, we must build on the progress we have seen in decarbonizing our economy. Such efforts would include market incentives to accelerate the transition already underway toward a renewable energy economy. We must also put a price on carbon to level the playing field in the energy marketplace so renewables can compete fairly. Such actionable goals provide a framework for making further progress in subsequent summits.

Michael Mann is distinguished professor of meteorology at Pennsylvania State University and author of “The Hockey Stick and the Climate Wars: Dispatches from the Front Lines” (with guest foreword by Bill Nye “The Science Guy”).

John Reilly: Be more aggressive

Climate change is accelerating. Is 2 degrees the right goal? Can we live with 3 degrees? Island states will disappear because of sea level rise with 2 degrees or less warming.

John Reilly
Picasa
John Reilly

Paleoclimate data show the sea level was 6 to 8 meters higher when polar temperatures were 4 degrees warmer. A 2-degree increase in global mean temperature would result in a 3- to 4-degree warming at the poles.