This year, World Habitat Day falls during the month when demographers predict our planet's seven billionth inhabitants will be born. The future that this child and its generation will inherit depends to a great degree on how we handle the competing pressures of growing population growth, urbanization and climate change. Experts predict that by the year 2050, global population will have increased by 50 per cent from what it was in 1999. Also by that time, scientists say, global greenhouse gas emissions must decrease by 50 per cent compared to levels at the turn of the millennium. I call this the "50 – 50 – 50 challenge."

Rising sea levels are a major impact of climate change – and an urgent concern. Sixty million people now live within one meter of sea level. By the end of the century, that number will jump to 130 million. Major coastal cities – such as Cairo, New York, Karachi, Calcutta, Belem, New Orleans, Shanghai, Tokyo, Lagos, Miami and Amsterdam – could face serious threats from storm surges.

The nexus between urbanization and climate change is real and potentially deadly.

Cities are centres of industrialization and sources of emissions, but they are also home to solutions. More and more municipalities are harnessing wind, solar and geothermal energy, contributing to green growth and improving environmental protection.

Local efforts are critical to success, but they must be supported by international initiatives. We have already seen progress, including the creation of the Climate Change Adaptation Fund and adoption of the action plan to Reduce Emissions from Deforestation and forest Degradation, known as "REDD plus." All countries agree on the goal of limiting global temperature rise to below 2 degrees Celsius. Developed and developing countries have committed to lower greenhouse gasses in a formal, accountable international agreement.

Now we need to build on these advances. The United Nations Climate Change Conference in Durban this December must achieve decisive progress. Urbanization will be on the agenda at next year's Rio+20 UN Conference on Sustainable Development.

On this observance of World Habitat Day, let us reaffirm our commitment to the important journey to a more sustainable future, and let us focus greater attention on addressing climate change in the world's cities and beyond.