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People changing climate
1. Man-made climate change?
- Changes in concentrations
- Changes in climate
- Inertia of climate
- Feedback effects
- Abrupt changes
* Worksheet 1
* Worksheet 2
2. How will future be?
3. How hinder climate change?

How are
people changing
the climate?

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1. Man-made climate change?


The inertia of
the climate system

One important characteristic of the climate system is its inertia that is, it takes a long time from when something happens (cause) to when we see the total consequences (effect). For example, it takes a very long time from:



  • when people emit CO2 or another gas until we can measure new stable concentrations of the gas in the atmosphere 
  • when the concentration of greenhouse gases increases until we can see the effect on the temperature 
  • when the temperature changes until we can see the biological effects in various species of plants and animals such as their extinction, mutations, or relocation to new habitats 
  • when the temperature in the atmosphere increases to when the sea level rises.

An illustration of this slowness can be the reduction of glaciers that has been measured in certain areas; although they have been reduced by about one-third over the last 135 years, this is mainly because the Earth is still returning to its normal state after a temporary cooling during the middle ages (the "Little Ice Age" from 1400 to 1800)!

Because the climate system is so slow, the climate will continue to warm up even after emissions are stabilized or reduced. The sea level will continue to rise for many hundreds of years after CO2 emissions are stabilized.

The slowness also adds to the uncertainties in our knowledge about climate changes. Both the degree to which people add to the greenhouse effect and the possible consequences of human actions are difficult to study because it takes so long from when a gas is emitted to when we can measure the changes. And when scientists try to estimate how the future will be, it takes a long time from when they make the calculations to when they can check to see if they were right.

SLOW RESPONSE: This figure shows what might happen if man-made emissions of CO2 stop growing at some point during the next hundred years, and then start falling. After CO2 emissions are reduced and concentrations in the atmosphere stabilize, surface air temperature continues to rise slowly for a century or more. Expansion of the ocean due to of warmer water continues long after CO2 emissions have been reduced, and melting of ice sheets continues to contribute to sea-level rise for many centuries. Source: IPCC (click to enlarge, 48 kB)

The slowness also means that the consequences of our actions are less noticeable now than they will be in the future. Emissions from one generation affect mainly future generations; and likewise, anything we do now to slow down climate change will only show results many years from now.


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Author: Camilla Schreiner - CICERO (Center for International Climate and Environmental Research - Oslo) - Norway. Scientific reviewers: Andreas Tjernshaugen - CICERO (Center for International Climate and Environmental Research - Oslo) - Norway - 2004-01-20 and Knut Alfsen - Statistics Norway - Norway - 2003-09-12. Educational reviewer: Nina Arnesen - Marienlyst school in Oslo - Norway - 2004-03-10. Last update: 2004-03-27.




last updated 11.07.2005 18:47:21 | © ESPERE-ENC 2003 - 2013