The current estimate for global temperature rise by 2100 is 3.5C. This is a devastating conclusion that underlines why many people, including myself, believe global warming represents the biggest threat to mankind. The international consensus that has emerged is that: global temperature rise should be limited to 2C; that emission policies should be determined at regional (eg. European), national and city level; and that the United Nations should monitor and co-ordinate these.

While a limited deal was reached at Durban, securing a comprehensive, global agreement is unlikely soon. A key problem is that governments are focused upon immediate issues such as financial fragility. There is also growing caution about long-lasting, tightly defined agreements that might affect flexibility.

Furthermore, some argue that an agreement is unnecessary because of future technological solutions, while another complicating factor is that many developing countries insist their economies must grow significantly before they can reduce total emissions.

Recent measurements are consistent with predicted effects in the atmosphere, ocean and on land caused by climate change. For instance, temperatures over land areas have steadily increased, while ocean surface layers in this decade have cooled especially over the Pacific. This is a long-lasting and natural cycle. But the deeper ocean has simultaneously been warming, resulting in a steady rise in global average sea level. In the tropical seas surrounding low-lying coastal areas the level is rising about three times faster, so local communities are at risk.

These and other disturbing phenomena are driving regional, national and city legislators to introduce bills and regulations to control emissions, preserve forests, marine areas and other critical environments. Moreover, 9,000 companies are working together and with governments to enable a framework for long-range investment.

Another positive is the high-level commitment by the UN and national governments to dealing with climate change which encouraged hundreds of organisations, engaged in practical programmes, to come to South Africa.

As the danger of international non-coordination is better understood, people will probably press governments harder for a comprehensive, global agreement. However, even such a deal will be useless without rigorous monitoring, and actions of governments and industry. High-level science and technology, and on-the-ground inspection, must also be foundations of the road map for tackling climate change.

Lord Julian Hunt is a visiting professor at Delft University of Technology, and vice-president of Global Legislators Organisation (Globe)