evidence: In new research, we show that lockdown had a negligible effect on global temperatures. So what really happened? [...] The different gases and aerosols we emit either contribute to global heating or global dimming. So determining how lockdown affected global temperatures is a matter of finding out which effect dominated. [...] The lockdown offered an invaluable test for our theories about how pollutants affect the climate. From this, we’ll be able to improve our models and make better predictions. We’ll also know better how to plan a strategy that reduces emissions from different sectors without inviting a sudden and sharp increase in global heating.