1/n A $100m carbon removal @xprize cool! But folks who care about climate should ask some hard questions.Virgin Earth Challenge $25m prize launched in '07 by @richardbranson. Original prize terms
1/n Earth system models are not 'just theory'. Models rest on observation and experiments that reach back over centuries. (Yay Tyndall!) Models use to assess solar geoengineering have errors that
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