3. Conclusion

The difficulty of taking account of uncertainties in the decisions to be made in the face of the risks of climate change impacts is a reality. The cost of climate change, without any mitigation measures, is estimated at a minimum of 5% of global GDP, and could reach 20%, whereas mitigation measures would cost only 1% of annual GDP. However, whatever happens to mitigation measures, we will inevitably have to adapt because the climate has already begun to change; ocean masses are moving and the CO ₂ injected into the atmosphere is trapped there for several decades. Also, without a reduction in greenhouse gas emissions, the state of the atmosphere is likely to reach a critical threshold beyond which adaptation could become extremely difficult, if not impossible. In other words, while adaptation will enable us to protect our societies from the effects...