Bill Hare, Potsdam Institute for Climate Impact Research; Harald Winkler, University of Cape Town; Julia P G Jones, Bangor University; Luke Kemp, Australian National University; Meraz Mostafa, Independent University, Bangladesh; Pep Canadell, CSIRO, and Stefan Rahmstorf, Potsdam Institute for Climate Impact Research
The Paris climate agreement, first struck in December 2015, enters into force today. The treaty commits countries worldwide to keep carbon emissions "well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C".
Countries will pursue self-determined emissions targets, agreed upon before the last round of climate talks, from 2020 onwards. The national targets will be reviewed and strengthened every five years.
The agreement also commits richer countries to provide funding to poorer countries, which have done the least to contribute to climate change but will suffer its worst effects.
As the world embarks on its most dedicated effort yet to prevent catastrophic climate change, The Conversation asked a panel of international experts to give their view on the significance of the agreement coming into force.
Bill Hare: 'A historic turning point'
For better or worse, the entry into force of the Paris Agreement is a historic turning point, humanity's most organised response to date to the largest and most far-reaching challenge to the habitability of the planet and viability of its life: human-induced climate change.
To me, this agreement represents our last best chance to come together and take the essential steps to prevent the worst consequences of climate change.
Over the next five to ten years, if we succeed in bending the present upward curve of emissions and ramping up climate action - meaning that by 2025 emissions are well and truly on a downward trajectory - then we will be able say the agreement is working.
In this timeframe CO2 emissions from coal would need to drop at least 25% below recent levels. We would also need to see a whole range actions towards a sustainable, fully renewable, zero-carbon future by 2050. Such an outcome is not beyond what can be imagined, as the necessary measures bring many benefits, and the technologies to get there are getting cheaper every month.
Make no mistake - we would still be confronting major climate challenges even if we limit global average warming to 1.5°C. But without that action our challenges would be immeasurably worse.
Should we not succeed, and emissions continue to increase, the Paris Agreement could come to symbolise all that is wrong with the world, and with the present world order. Such an outcome would be associated with other large-scale societal problems, such as rapidly increasing economic inequity, as well as access to political power and decision-making. Unchecked climate change would exacerbate many of these issues, including the increasing likelihood of climate-induced migration.
Scientists and policy makers are mobilising now to help in the next great stage of implementing the Paris Agreement, which is to increase the level of ambition and action. An IPCC Special Report is being organised for 2018 to assess impact, mitigation, and sustainable development issues surrounding the 1.5°C temperature limit.
This report will provide vital input to the 2018 facilitative dialogue, organised by the UN's climate change organisation, which is meant to examine how countries' global aggregate level of action stacks up against the required emission pathways in 2025 and 2030. The results of this dialogue will provide guidance to countries as they prepare to submit their updated, and hopefully upgraded, nationally determine contributions by 2020.
Julia Jones: 'Forest people cannot bear the costs'
The loss of tropical forests contributes as much as 10% to global emissions of greenhouse gases. For this reason (and because protecting rainforests has other potential benefits), a UN-negotiated mechanism on Reducing Emissions from Deforestation and Degradation, known as REDD+, is widely promoted as an important pillar in efforts to tackle climate change.
Since the idea that tropical forest nations should be funded to slow deforestation was initially proposed in 2005, many initiatives have sprung up to explore how REDD+ can work in practice. These pilot schemes show that while well-designed projects can deliver emissions reductions, conserve biodiversity and improve local livelihoods, positive outcomes are far from guaranteed. A number of groups advocating for the rights of people who live in forests strongly oppose REDD+, as they believe that it will result in evictions.
As of today, efforts to slow climate change by saving rainforests are enshrined in international law via the Paris Agreement. What will this actually mean for tropical forests and its people? Resources available for conservation will increase, which is certainly positive.
However for millions of people, mostly very poor and politically marginalised, these forests are home and the source of their livelihoods. Their needs, views, and knowledge must be taken into account in any conservation actions. It cannot be fair that forest people bear the costs of mitigating climate change.
Luke Kemp: Watch out for Donald Trump
The Paris Agreement's entry into force is both impressive and troubling. It could be a sign of renewed international momentum. But its speed is more likely indicative of a lack of substance.
Ratification means few legal obligations for participating countries. Paris entering into force has more symbolic than legal strength.
What does entry into force mean for those nations that have not joined, such as Russia? Not a great deal for now. Arguably, they should be excluded from having a voice and a vote in initial negotiations over the finer details of the agreement's implementation.
In practice, diplomats are eager to ensure that Paris remains a truly global effort, and have created a technical workaround so that even countries that are yet to ratify can participate in discussions. The (perhaps naïve) assumption is that eventually all parties will join.
In the longer term a lack of ratification is likely to lead to exclusion from discussion under the Paris negotiations, as well as an inability to use elements such as market-based mechanisms under the agreement. Non-ratifying countries will probably also become international pariahs.
However aside from social pressure, the Paris Agreement is extremely weak against countries who choose not to join, or opt to withdraw. It contains no "non-party" measures to entice participation or punish non-ratifying countries. Such an arrangement looks fine for now, but it could become a fatal flaw if Donald Trump takes power in the US on November 8.
Paris was designed to be a universal agreement that appeals to the United States, trading away strong substance in favour of quick approval and universal participation. A rogue superpower could mark the end of the honeymoon.
Meraz Mostafa: 'New approach to climate policy'
With the activation of the Paris Agreement, the issue of loss and damage becomes a central tenet of international climate governance. The UN climate body is now committed to address the impacts of climate change that go beyond adaptation. These include everything from islands sinking in the Pacific Ocean to infrastructure damage during cyclones.
This is somewhat surprising given how contentious the issue of loss and damage has been at climate talks. Arguably, the first reference to the concept was proposed in 1991 by Vanuatu, whose negotiators unsuccessfully argued for an international risk insurance pool to deal with the adverse affects of climate change.
But it took until 2014 for the UN climate body to establish a separate mechanism, called the Warsaw International Mechanism. This mechanism consists of nine action areas ranging from how best to finance loss and damage to how to deal with the impacts of climate change not easily valued in the market (the loss of home, tradition, culture and so on).
Even with this in place before the Paris negotiations last year, several developed countries, including the US, were uneasy about including loss and damage in the agreement. This is because they were worried this issue would quickly bring up the question of whether developed countries could be held liable and have to compensate for their share of greenhouse gas emissions. A comprise was reached in negotiations where a separate article in the agreement was dedicated to loss and damage, but the notion of compensation and liability were explicitly ruled out.
The article on loss and damage in the Paris Agreement mainly focuses on supporting the Warsaw mechanism. The next round of climate talks in Marrakesh will be important, because it is when the negotiators are expected to come to a decision on a five-year rolling working plan for the mechanism.
This plan is yet to be determined, based on the last meeting of the executive committee of the Warsaw mechanism (made up of an equal number of representatives from developed and developing countries). In particular, separate task-forces will be created to address issues such as migration and non-economic loss and damage. An information hub for comprehensive risk management (that is, microinsurance) will also be established.
The Paris Agreement is significant, because it establishes a new approach to climate policy, whereby climate change-related loss and damage will have to be addressed alongside mitigation and adaptation.
Stefan Rahmstorf: Governments should be in emergency mode
The Paris Agreement is the best we could have expected at this point in history. It is a beacon of hope. Almost all nations on Earth have decided to move towards net zero emissions.
It was high time, and in some respects too late. Paris came almost exactly 50 years after the famous Revelle report from the US president's scientific advisory panel issued a stark warning of global warming, melting ice caps and rising seas due to our carbon dioxide emissions.
The long delay in confronting this threat is not least a result of a major, still ongoing obfuscation campaign by fossil fuel interests.
The goal of the Paris Agreement to limit global warming to 2°C, or better 1.5°C, is necessary. Two degrees of global warming is very likely to spell the end of most coral reefs on Earth. Two degrees would mean a largely ice-free Arctic ocean in summer, right up to the North Pole.
Two degrees would be very likely to destabilise the West Antarctic ice sheet (evidence is mounting that this has already happened). Such an increase might even destabilise the Greenland ice sheet and parts of the East Antarctic ice sheet, locking in more than ten metres of sea-level rise and sealing the fate of coastal cities and island nations.
Some major impacts of our fossil fuel burning cannot be prevented now, thanks to the fateful delays already mentioned. But every 0.1°C of warming we avoid helps contain further massive risks to humanity, including major threats to food security.
Because of all the time that was lost, the remaining emissions budget is very tight: at current rate, we are eating up the budget to stay below 1.5°C (with a 50:50 chance) in about ten years. The budget for 2°C would allow us to keep emitting for about 30 years. If we ramp down emissions rapidly we can stretch these budgets out to last longer, but the key here is to turn the tide of emissions now or we can give up on staying well below 2°C.
If we take the Paris Agreement seriously (and we should), governments around the world should be in emergency mode, taking rapid and decisive measures to get their emissions down.
Pep Canadell: Little time for celebration
By all accounts, the Paris Agreement is an astonishing achievement. However, we should spend little time in celebrating its coming into effect and move swiftly from the broader well-intended rhetoric to specific actions. The next round of climate negotiations, beginning in Marrakesh on November 7 will be the first real test to assess how committed countries are to the goals of the Paris Agreement.
Each individual country needs to show how they will specifically implement the very vague National Determined Commitments, and equally important, how they are planning to go beyond those initial commitments, now that we know that the collective effort falls well short of what is required to stay below 2°C.
Harald Winkler: 'Implementation of adaptation and mitigation needed'
The Paris Agreement has entered into force. The global significance is the political momentum for climate action continues. From a southern African perspective, the implications for adaptation are at least as important as mitigation - and both will need support. The focus must shift to implementation at the local level.
For Africa, the Paris Agreement gives much greater political visibility to adaptation. Article 7 includes a global goal for adaptation. But also a review to ensure that the adaptation response is adequate. The adaptation goal links the temperature goal - to be held below 2°C, and pursuing efforts to 1.5°C above pre-industrial levels - with adequacy.
The greater the increase, the worse any negative impact will be, particularly for African countries with low adaptive capacity. International practice on adaptation needs enhancement, this can build on existing methodological work, particularly on information for the adaptation component of Nationally Determined Contributions or other forms of communication.
To take effective adaptation action locally, the adaptation finance gap must be addressed.
Certainly all countries will have to do more on mitigation. The literature is clear that the sum of the Intended Nationally Determined Contributions "still imply a median warming of 2.6-3.1 degrees Celsius by 2100". This is often simplified to mean more mitigation, but in many southern African countries, this will mean "avoided emissions". The challenge is to follow development pathways - to meet basic developmental needs - without going to high emissions in the first place. Avoiding a high-emissions development pathway is a big ask of African countries.
Support is essential to shift to both low carbon and climate-resilient development pathways.
The strength of the Paris Agreement lies in its comprehensive scope that includes finance, technology and capacity building. The success of local action on adaptation and mitigation depends on implementing these provisions. For the first time in global climate governance, developed countries have agreed to communicate indicative support to developing countries every two years ex ante. Access to environmentally sound technology and capacity building will be important to achieve the necessary transitions. Continuous support for the Capacity Building Initiative for Transparency is a crucial aspect of transparency; and transparency related capacity.
Finally, local action is needed - and, globally, a multi-lateral rules-based regime, which is what the world set out to achieve in Durban and agreed in Paris. Fully developing the Paris "rule book" is a key task at the international level. But we dare not wait - each country and all its people need to start to prepare for the impacts, avoid emissions and where emissions are high, reduce them very rapidly indeed.
Bill Hare, Visiting scientist, Potsdam Institute for Climate Impact Research; Harald Winkler, Professor and Director of the Energy Research Centre, University of Cape Town; Julia P G Jones, Professor of Conservation Science, Bangor University; Luke Kemp, Lecturer in International Relations and Environmental Policy, Australian National University; Meraz Mostafa, Research officer, International Centre for Climate Change & Development, Independent University, Bangladesh; Pep Canadell, CSIRO Scientist, and Executive Director of the Global Carbon Project, CSIRO, and Stefan Rahmstorf, Professor of Physics of the Oceans, Potsdam Institute for Climate Impact Research