Climate Change

Climate Change Key Facts

Mainstream scientists agree that climate change is real and will have significant impacts on our planet and therefore on how we live in our cities. Some key facts about climate change follow.


 Key Climate Change Key Metrics:

  • 250 ppm – pre-industrial levels of CO2

  • 390 ppm – is where we are today

  • 2 ppm – yearly increase in CO2e

  • 2 degree C increase in earth’s average temp above pre-industrial level before deadly feedbacks kick in

  • 450 ppm – IPCC sustainable concentration

  • 350 ppm - The sustainable concentration of CO2 now estimated by respected climate scientists 


Although many climate scientists agree that we must not pass the 450ppm level of CO2 in order to remain within the 2-degree band of sustainability, there are a growing number of climate scientists that think that the 350ppm level (originally proposed by climate scientist James Hansen) is a more reliable number.  Until 200 years ago, the CO2 atmospheric loading was 250ppm. Today it’s 390 and rising at 2ppm annually. We only have a few years before we reach the 450 mark, and we now well now past the 350 ppm level of safety!


Key Climate Change Impacts:

  • More energetic violent weather and its associated costs

  • Greater demands on existing aging infrastructure

  • Coming economic costs of carbon mitigation

  • Less arable land and increasing food costs

  • National and regional resource conflicts

  • Migrating populations - out of impacted areas


It is now clear that three things are needed to avert the 2-degree rise and its disastrous consequences:

  1. The world’s governments need to sign and implement Carbon Capping treaties to cap and then invest heavily in the development of both renewable energy technologies and strategies, as well as in energy conservation strategies to reduce absolute carbon dioxide emissions. To be effective, these pacts must bring atmospheric levels of CO2 back to 350ppm of CO2 equivalent green house gases over the next 50 years.
  2.  Large cities, and their inhabitants are now responsible for the majority of CO2 emissions. Cities will have to be the focus of strategies for significantly reducing their CO2 emissions.
  3. Because CO2 stays in the atmosphere for hundreds of years, and the current levels are about 387ppm, strategies will be needed to control and offset temperature rise until the treaty effects are felt. These strategies, called geo-engineering, will be aimed at bringing CO2 loading down to 350ppm.


More about the economic consequences of climate change at World Bank Climate Report >>

More about temperature trends, effects and tipping points at 350.org >>

Links to books and sites on political scenarios >>