Time is running out – NZ scientists say why limiting global warming to 2degC is important

As delegates at the United Nations climate change conference in Durban, South Africa, negotiate what — if any — binding agreement replaces the Kyoto Protocol on global warming, New Zealand experts have set out why it is crucial that nations rise to the challenge of limiting global warming to 2degC.

Though the previous Copenhagen and Cancun conferences agreed that future global temperature rises should be kept to this margin above pre-industrial levels, that target was merely ”recognised” by the participants, not formally adopted.

Now delegates from 195 countries — including New Zealand’s Minister for International Climate Change Negotiations, Tim Groser, and Climate Change Minister Nick Smith — are trying to pull together a emission-reduction commitment binding on all developed countries as well as advanced and major-emitting developing countries.

Separately, scientists working on the Global Carbon Project have said that despite nearly 15 years of pledges to make cuts, the release of carbon dioxide from the burning of fossil fuels is still increasing at a record rate.

Global emissions rose by 5.9 per cent in 2010, nearly twice the average increase of the past decade. Much of the 5.9 per cent  global increase from 2009 to 2010 was due to increased emissions from the world’s largest fossil-fuel emitter, China, where emissions rose 10.4 per cent, while India’s rose 9.4 per cent. Emissions from developed countries jumped 3.4 percent.

Mr Groser said: “Only a comprehensive agreement will make a real difference to climate change”.

Today the New Zealand Climate Change Centre released a six-page explanation of why that “real difference” targetting a 2degC limit on warming will require a global programme to cut net greenhouse gas emissions to near zero over the next 80 or 90 years.

The science brief The Challenge of Limited Warming to Two Degrees was written by Dr Andy Reisinger, of the NZ Agricultural Gas Research Centre, Richard Nottage of the Climate Change Centre at NIWA, and Judy Lawrence, a senior research associate at Victoria University’s Climate Change Research Institute.

You can read it below:

Dr Reisinger responded to questions from the SMC:

What realistic chance remains for a tougher limit of 1.5degC average temperature rise above pre-industrial levels, which 194 nations agreed at Cancun in 2010 to consider at a future review?

“As we note in our Science Brief, the chances to limit the temperature increase to 2degC are diminishing, so the chances to limit the increase to 1.5degC are even smaller. Ironically, waiting a few years before considering an even tougher target will make it even harder to achieve this tougher target, given that continued delays are the reason why even the 2degC limit is rapidly becoming less feasible.

Personally (considering the lack of progress in international negotiations and lack of implementation of stringent climate policies in most world regions) I believe there is no realistic prospect that we won’t overshoot the 1.5degC limit for some considerable period of time during the 21st century.

“A possible exception would be if we get a welcome but very unlikely surprise from the climate system itself, that is, if by sheer luck its sensitivity to greenhouse gases turns out to be at the lowest end of published science-based estimates. The other exceptions are economic or social crises that derail human development and thus reduce future greenhouse gas emissions on a global and long-term scale.

“However, this does not mean that we are doomed to a much warmer world forever, as it may well be possible to bring temperatures down to 1.5degC above pre-industrial levels in the long term (beyond 2100) even if they have been exceeded temporarily.

This could be achieved through technologies that can actively take carbon dioxide out of the atmosphere again, either by widespread use of bioenergy and capturing and storing the carbon dioxide emitted when biofuels are burnt; or by chemical processes that directly remove carbon dioxide from the atmosphere in such a way that it can then be stored underground.

The ability to do this at sufficiently large scales remains speculative though, as it has to manage either competing land-use between biofuel, food production and maintenance of permanent indigenous forests to maintain biodiversity, or the increased energy demand for the chemical removal of carbon dioxide.

“Both are theoretically possible pathways (in combination with stringent emissions reductions – they can’t substitute for them), but neither offer a reliable or tested path. Nonetheless, they appear the only feasible options still open to achieve the goals that countries have collectively agreed they wish to meet, given that it appears impossible to find a political agreement and collective policy actions that would result in the rapid emissions reductions required to avoid substantially overshooting the 1.5degC and even 2degC limits in the first place”.

Even if all the present pledges (up to the Durban talks) to cut emissions are honoured, longterm average temperature rise will still exceed 3degC: What are the implications of this for our children and their children?

“Personally I’d characterise the difference (from a global perspective) between accepting 2degC and more than 3degC warming as that between risky and outright reckless.

“With greater warming, the risk of severe impacts increases, and the ability to adapt to changes successfully reduces in many regions of the world and for many sectors. The difference between 2degC and 3degC warming can mean the difference between managing ecosystem change and losing a species or entire ecosystem.

“It can mean the difference between managing increased droughts and forced fundamental change in land-use because agriculture is no longer viable. It can also mean the difference between enjoying benefits from a smaller degree of warming in temperate regions (e.g. extended growing seasons, lesser winter health issues) and trading those off against greater invasion of warm-adapted pests and diseases, or increasing summer heat waves and their health implications.

“But, as we note in our Science Brief, we generally cannot draw a clear and single line that says this or that impact definitely will happen at 3degC but definitely won’t happen at 2degC. For this reason, even if we fail to limit warming to 2degC, this is not a reason to give up, as it would still be better to limit warming to 2.5degC than to allow it to go above 3degC.

“It’s also worth noting that a lot of impacts are projected to happen at warming of even less than 2degC – witness the floods in Australia and Pakistan, bushfires in Russia, and heat waves in many parts of the world during the last couple of years. Such events are expected to gradually become more frequent with any amount of warming, not just once we’re beyond 2degC.

“Perhaps the most fundamental difference between less than 2degC and more than 3degC warming are the risks for fundamentally changing the way the Earth’s climate system works.

“At more than 3degC warming, the chances of losing most of the Greenland and West Antarctic ice sheet are substantially greater than below 2degC, and it will take much longer to bring temperatures down again to levels where we can consider those ice sheets to be reasonably safe from complete disintegration.

“But here again, we can’t give exact temperature thresholds – the main thing is that risks increase with higher temperatures, and we are ever more pushing into a territory that the world has not been in for millions of years”.

Remaining opportunities to limit warming to 2degC are rapidly diminishing: what are some of the global trade-offs the world would have to make for continuing the present GHG emissions patterns until  the 650 gigatonnes “buffer” is exhausted?

“The key point from most model studies (and common sense) is that a gradual change in emissions is less disruptive than exhausting the budget and then falling flat on our faces.

“There is very robust evidence that we can limit emissions such that temperatures will increase by no more than 2degC without breaking the bank and without halting economic growth and social development in developing (or developed) countries.

“But to achieve this requires globally concerted actions and full implementation of all available mitigation options through consistent and durable policies.

“There are plenty of mechanisms by which the financial implications of stringent mitigation actions could be shared such that no single country or group of countries face an unacceptable burden; the (as yet unmet) challenge is to show leadership and develop sufficiently broad alliances that can turn these potential solutions into reality”.

Limited warming could give better river flows for some NZ hydro-electric dams, and farmers could gain longer growing seasons. To what extent do you worry that New Zealanders living in a temperate, maritime climate will fail to see the longterm and global downsides of climate change?

“A key challenge in dealing with climate change is that its implications can differ a lot between regions and sectors, and yet there is only one planet with one global climate system that we share. Understanding and accepting this global interconnectedness is a key issue.

“New Zealand may be less hard hit by future climate change than many other countries, and will even see some initial benefits. The global interconnections go even further: every time there is a major drought somewhere on the planet, this tends to drive up commodity prices and producer returns in New Zealand increase”.

“But these benefits are quite specific to some sectors and regions; the negative implications to e.g. housing and infrastructure from sea level rise, to farming in drought-prone regions, to native species and ecosystems, are just as great as anywhere else and can be harder to manage given the small size of our country and more limited resources”.

“Dealing with this complexity can occur along two lines of thought. One is simple common sense: New Zealand relies on a functioning world and domestic economy that is positively disposed towards free trade and flow of goods and services. A perception of New Zealand as a smirking free rider on the efforts, let alone misery, of others (or the perception of the free riding of some sectors within New Zealand) could do substantial damage to our economic development and social cohesion and well-being.

“The other thought, linked to the first, is the inescapable ethical dimension: I don’t believe one can fully rationalise why a country that may be less hard hit by a collective problem should engage fully in reducing its contribution to this collective problem.

“One can mount a lot of rational arguments such as the above, and support them with economic and social analysis, but at the end there remain irreducible ethical grounds that motivate reductions of greenhouse gas emissions. But, given that people display different ethical choices and preferences every day in their interactions, this also means that it is very hard to find a robust and sustainable consensus on what the ‘right’ level of action should be”.