The expression global warming mostly evokes mental pictures of melting ice sheets, dying coral reefs and failing crops in parched rural landscapes. We see a planet fraying at its pristine edges.
But it is in the cities not rural areas where the most effective action to curb and adapt to climate change caused by global warming is felt. Moreover, experts say that the bulk of the population growth over the next century will happen in cities in poor and middle-income countries.
Therefore, Africas growing cities could hold the worlds future in their hands. They could either exacerbate global warming by choosing their development paths poorly or provide solutions by choosing sustainable development pathways.
Summer in the city
It may not come as a surprise that cities, with their cars, industries and throngs of people, are key actors in the global climate game.
However, what may be surprising is that the UN Intergovernmental Panel on Climate Change (IPCC)s recently published Fifth Assessment Report on impacts, adaptation needs and vulnerability of climate change is the first in the panels series to have a chapter focusing on urban areas. 
Cities are major sources of greenhouse gas emissions and consume a lot of global resources, according to the report, published last month (31 March) in Yokohama, Japan after a five-day meeting of hundreds of scientists and policymakers to hammer out the details of the document.
However, cities also house more than half of the worlds population and the bulk of global economic activities. That makes them vulnerable to myriad of climate-related risks from global warming, such as water and food scarcity, disease outbreaks and sea-level rise.
Therefore, cities offer both risks and opportunities for the global environment, the IPCC report says. Improved basic services and housing for the poor, combined with more climate-smart planning of things like roads, residential areas, power and water supplies have a great potential to accelerate climate change adaptation globally.
There is already plenty of initiative to green the worlds big cities. The C40 cities project, a network of 40 big cities launched in 2005 by Londons then mayor Ken Livingstone, brings 40 megacities across the world together in actions to reduce greenhouse gas emissions. African cities participating in the project are Addis Ababa in Ethiopia, Cairo in Egypt, Cape Town and Johannesburg in South Africa, Dar es Salaam in Tanzania, Lagos in Nigeria and Nairobi in Kenya
However, according to the IPCC report, it is not these megacities that can make the biggest difference to the climate change scenarios of the future.
Rather, it is the cities in Africa, Asia and Latin America that currently have less than a million inhabitants where most population growth is expected over the next few decades.
Unfortunately these cities local governments have scant capacity to promote green development planning. There is also limited interaction between research institutions that are pioneering sustainable solutions and such municipalities.
Debra Roberts, a researcher who works on environmental planning in the eThekweni Municipality of Durban, South Africa, believes local governments hold the key to climate-smart development in Africa.
Cities offer us one of the single best opportunities for adaptation, says Roberts, who was a lead author on the IPCC reports chapter on urban areas. The one most urgent thing right now is to give local government a mandate to act on climate change issues.
Gaps in the data
There is still a lot of research to be done to understand the best ways in which these mid-size cities can beat the path to a sustainable future.
One challenge that Roberts and her co-authors faced was the relative lack of peer-reviewed research on urban climate change and action. They had to draw on a lot of so-called grey literature material published by NGOs such as the UK-headquartered Oxfam and local municipalities to complete the new chapter.
The knowledge is often locked up in local governments in Africa and elsewhere, Roberts says. She would like to see more of this information make it into the peer-reviewed literature so that city planners have a stronger evidence base on which to peg their policies.
This, of course, mirrors the wider challenge of data-scarcity for modelling climate change and global warming effects in Africa. But at least the dataset is getting better, climate scientists agree.
In order to plan for the future, Africas decision-makers and citizens need as clear a picture as possible of what effects climate change may have in their areas, and the best ways of dealing with it.
Growing cities, and their management, are going to be an important piece in Africas climate puzzle.
Journalist Linda Nordling, based in Cape Town, South Africa, specialises in African science policy, education and development. She was the founding editor of Research Africa and writes for SciDev.Net, Nature and others.
This article has been produced by SciDev.Nets Sub-Saharan Africa desk.