We are facing an urban future in the 21st century, with more than half of the global population now living in cities. With cities already accounting for 75 per cent of world final energy use and 76 per cent of carbon dioxide emissions, there is increasing global attention on how we plan and design our urban settlements to reduce emissions and adapt to the impacts of climate change. With the very active engagement of sub-national governments and mayors, COP23 provides a unique opportunity for nation states to work more closely with cities to plan for climate change. 

The 2015 Paris Agreement explicitly mentions 'cities and subnational authorities' as one type of non-party stakeholder that is invited to 'scale up' its efforts. On 11 November, planners throughout the world will unite to launch 'Planners for Climate Action' as a global commitment to work together on implementing more sustainable solutions for our urban future in the 21st century.

COP23 increases the international pressure for Australia to meet its COP21 commitments. Australia presently has no climate policy, no effective renewable energy policy, no coastal policy for coastal climate change (sea level rise, storms), and no national urban policy for more sustainable cities. In summary no national sustainable development strategy that can implement the COP21 Paris Agreement and the UN Sustainable Development Goals that we have signed on to in an integrated way for the long term benefit of communities and the environment. No plan for a more sustainable future. 

I expect there will be a showcase of leading practice by cities on display in the Bonn NGO zone, together with governors, mayors etc., which will the positive story coming out of COP 23: a groundswell of local action emerging across the globe. Change is coming...

During COP23, Australian scientists will raise their voices, and campaign for the transparent use of evidence and evidence-based practice in global climate action. In this era of alternative facts, and considering national issues on the radar like the destruction of the Great Barrier Reef and our absence of long-term climate strategies, this focus is more important than ever.

One point of optimism is Australia's youth in environment and sustainability, who not only see scientific evidence as fundamental but wish to be the knowledge-brokers and boundary-spanners who can integrate this with an awareness of social, economic, and political languages, contexts, and sciences to gain traction on a global scale. The young scientists of today already have ambition - to use their science outside of the lab. We need to think about how we can best support and train them to be the interdisciplinary change agents they aspire to be.
 
Higher education has a crucial role to play in preparing these future scientists with the broader interdisciplinary skills and global and cross-sector awareness to contribute meaningfully and with traction. Young scientists need to be trained to function effectively as change-agents in forums such as COP23, in order to engage with politics, economics, and social aspects of sustainability to make the difference they aspire to. Young sustainability leaders, working locally or globally, need the interdisciplinary capacity to know where science fits in the big picture, how to integrate it, and ultimately how to contribute more to global understanding.

Even if our CO2 emissions were to be halted today, the natural carbon cycle will likely take centuries to reverse the damage done in the past few decades, during which time we will continue to experience the negative effects of climate change. Thus, methods of removing CO2 directly from the atmosphere have been recognised as being critical to the success of any attempts at climate change mitigation.
 
As a joint venture between School of Chemistry and the Department of Chemical Engineering at Monash University, we are researching on developing a novel process for capturing CO2 directly from air using solar power as the only source of energy. Within the next two years we hope to construct Australia’s first pilot scale facility for capturing CO2 from air.

The next round of international climate talks ( UNFCCC COP23), hosted by Fiji, will kick off on Monday 6 November in Bonn, Germany. It will occur against a background of both accelerating climate change impacts as well as accelerating progress in responses, particularly energy transitions.
 
The hosting of this COP by Fiji (the first time by a small island state) will bring a renewed focus on the Pacific and the impacts of climate change on small island states. A key element of COP23 will be designing the Facilitative Dialogue (also called the Talanoa Dialogue) which will assess global progress towards the Paris Agreement goals and the additional steps needed to achieve these, profile opportunities to enhance action to address climate change and encourage further commitments to take action.
 
This COP will also progress the development of the Paris Agreement implementation guidelines (the ‘rulebook’) including the transparency framework which covers the reporting and review obligations. The meeting is anticipated to further highlight the constructive roles that the business sector, cities and civil society organisations are playing in developing timely and effective climate responses.
 
Since President’s Trump’s announcement on June 1 that the US would pull out of the Paris Agreement, there is likely to be some evolution and clarification of the role of the US will play and whether other countries will step up as climate leaders.

The international climate change negotiations in Bonn next week will be the first major meeting since President Trump announced that the US will withdraw from the historic Paris Agreement.

While recent comments from US officials suggest that it may be open to negotiations to remain in the agreement, European officials have been quick to dismiss this possibility.

The question now is who will lead global climate action in the US’ absence?

Australia should work with China and Europe to lead international efforts to reduce greenhouse gas emissions.

China is now the world’s number-one energy consumer and greenhouse gas emitter, and should it combine forces with Europe it has the potential to lead the world and prevent other nations from following the US down the path of inaction.

COP23 is being considered as the ‘Islands COP’, with Fiji holding the COP presidency and providing more opportunities for small island developing states to place their concerns at the forefront of international climate change discussions.
 
Importantly, it will place these small island states in a strategic position to influence international climate change policy, namely the Paris Agreement’s roadmap, which is set to take center stage.
 
The roadmap is of particular significance for small island states and other vulnerable nations as it outlines the steps needed to support the Agreement’s ambitious task and put the world onto the 1.5°C track.
 
Studies on climate change impacts released since the Paris Agreement in 2015 show dramatic implications for small island states and other vulnerable nations if global temperatures are to rise beyond the 1.5°C mark.

In 2014 the UN Climate Summit announced the New York Declaration on Forests, which aimed to cut deforestation by half by 2020, and end it all together by 2030. This declaration, and the fact that forest degradation has been so severe in Fiji, which presides over the COP23 meeting, suggests that forests, and agroforestry, will be a topic to be revisited next week.
 
Forests and trees are important for much more than carbon sequestration and provision of timber.  One factor which remains unclear is how forests contribute to the process of land surface cooling, and the generation of rainfall, both of which are important components of all climate models. 
 
Furthermore, due to the diversity of techniques of defining and measuring forest cover, (satellite data, FAO forestry databases, review publications etc.),  and other metrics of forest health, an exact measurement of  the extent of forest cover globally, and the sequestration services they provide, is still not available, with different institutions and nations using different criteria for judging what should be defined as a forest (should it be 70 per cent closed canopy cover, as originally used in Australia, or should it be 30 per cent closed canopy cover as required by the definition of bodies such as the UN FAO). 
 
While we understand the processes of evapotranspiration, where water passes through plants, absorbing CO2 from the atmosphere, we as yet fail to reach widespread agreement about what specific effect forest health has at the landscape scale, for example on evapotranspiration. Until this can be more effectively embedded into climate models, uncertainties associated with human impacts upon the climate will only increase.
 
Without more accurate science on the effect of tree planting and removal, afforestation programmes may well lead to unintended consequences, while calculations of carbon sequestration rates will be flawed. Both of these weaknesses will give rise to clear policy failure, providing ammunition for climate sceptics to create doubt in the minds of the public and policy makers.  This is important, not only for Australia with its fragile ecology, but also for all other countries of the world struggling with their agriculture in the face of global change.

While politicians can work behind the scenes to nullify the 'Trump effect', science has a duty to work towards consensus on what we really mean when we talk about the role of trees and forests on the climate system of the Earth.