21/12/2015 05:20 GMT | Updated 20/12/2016 05:12 GMT

A New Climate Deal

Last week I returned from COP 21 after nearly two incredibly busy weeks in Paris. Where I was promoting Bristol and negotiating a global solution to one of the biggest challenges that ours and future generations face.

Last week I returned from COP 21 after nearly two incredibly busy weeks in Paris. Where I was promoting Bristol and negotiating a global solution to one of the biggest challenges that ours and future generations face.

When I was leaving I must confess that I was unsure we would reach a solution but we now have. There was a last minute flurry of activity this weekend and an agreement was reached amongst world leaders that tackles climate change.

As many of you will know it is my ambition to make our city the greenest one in the world. I am delighted that it is now not just cities that are tackling this crisis but the whole world is following what we have done. We have at long last reached a critical mass of scientific, political, public and private opinion required to make change a true possibility.

I am proud that in Bristol all political parties have united to up our ambition, as a direct result of our involvement in COP, in making us a carbon neutral city by 2050. I would like to say thank you to the Greens, Labour, Conservatives and Liberal Democrats for putting party politics to one side on this very important issue that sits far above any political agenda.

This is a big goal that reaches beyond our pre-COP target of 80%, but when the agreement was reached in Paris on Saturday it became a feasible option for Bristol. Because with the outcome of COP21, we can be confident that the inventive and financial resources of the world will be aligned to this common goal, driving the policy, investment and technical progress required to achieve widespread decarbonisation.

With that said, we also know that the agreement will need to be strengthened in future years. Its flexibility may have made it possible for everyone to sign-up to, but ultimately issues will need nailing down in no uncertain terms. Among them are further reductions in carbon emissions pledged by each country, a firm date to end fossil fuel use and additional financial help for developing nations to adapt to the impacts of climate change caused by the industrialised countries, along with help for them to develop in a low carbon way. I will continue to push this agenda locally, nationally and internationally.

And we also know that there are powerful industries that will seek to slow down and undermine this agreement as they have for many years.But the tide has turned and it is now unstoppable. The world is aligned around the principle and has made a very public statement of intent.

Key to success will be the role of cities and regions as the main producers of carbon and the places closest to both the issues and solutions. We were included formally for the first time at this COP, and as European Green Capital, Bristol was delighted to co-host our presence alongside Marie Du Paris and ICLEI, the global local government sustainability network. Our contribution has ensured that the crucial role of cities and sub-national government has been enshrined in the global agreement. So in the UK and in every country, city councils and local people will be better able to engage with their governments. That could be through greater devolved powers or improved funding mechanisms.

We are now clear about what we have to achieve in Bristol and the UK and can design policies to achieve this, whilst also delivering many other benefits - for example cleaner air and an overall healthier environment for us and our children to live in.

We have also learned that cooperation is not only essential to our success but possible on an unprecedented scale. Locally we've had great success with the Bristol Green Capital Partnership bringing over 850 businesses, communities and others together to take action in their city. Now we have greater options for cooperation nationally and internationally, whether it is with the UK government or us learning from and co-operating with other cities, such as past and future European Green Capitals.

Bristol is well placed to not only deliver on our responsibilities as a global citizen, but also to prosper from the transition to a fossil-free era - with world leading businesses in the renewable energy, environmental and green-tech sectors. We'll do all we can to continue setting an example and sharing our lessons locally, nationally and internationally. Excitingly, the audience for that and potential for strong collaboration and progress just got a whole lot bigger.