Pierrehumbert objections to marine cloud brightening
SALTER Stephen
Dear Raymond
The reasons you give in today’s Guardian article by Amy Fleming as objections to marine cloud brightening are in fact strong arguments in its favour. Weather patterns do indeed depend on ocean temperatures which are now being changed by human activities. Marine cloud brightening used in the right time and place can put sea surface temperatures back to where they used to be. If we knew enough about the climate system, especially the wind speed and direction a few days ahead, we might even make thing more benign. We do know that the temperature gradient across the Indian Ocean sets the balance of floods and droughts between Africa and Australia. This could be adjusted by moving fleets east or west. We know that higher temperature affects the intensity of hurricanes and typhoons. Wherever we use marine cloud brightening will slow or reverse sea level rise.
You also object to the short life of the increased aerosol and the need to keep treatment for ever. I would be much more worried about anything that was irreversible. The short life gives a high frequency response and low phase lag which is desirable in every control system. It allows rapid correction of mistakes as we learn to how to do the control. We do not have to do it for ever, only until CO2 concentrations have been reduced. We do not interfere with any of the other climate solutions listed by Amy Fleming and we should use every tool in the box in parallel harmony. The spray vessels do not use fuel and are autonomous so, once you have paid for them, it is cheaper to keep them moving out as sea rather than paying harbour dues.
Breathe safely
Stephen Salter
Emeritus Professor of Engineering Design
School of Engineering
Mayfield Road
Edinburgh EH9 3DW
0131 650 5704
https://www.youtube.com/watch?v=ZBB6WtH_Ni8