Emeritus Professor Michael J Kelly, of Cambridge University has a warning: "if one concludes that the 2050 Net-Zero Emissions Economy cannot be achieved on scientific, materials, engineering, planning and financial grounds, it would be appropriate to reset the target to one that can be achieved, even at a stretch. With a changing climate, there may come a day when we need to act, just as we needed a Thames Barrier to prevent London flooding. It will be no excuse then that all the money was invested on projects to mitigate climate change, when the very need to adapt will be proof that the mitigation actions have failed."

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