An arm of billionaire Tom Steyer’s investment firm Galvanize Climate Solutions will begin buying and upgrading property across the US this summer and fall, aiming to cut the portfolio’s greenhouse gas emissions to net zero in three years without the use of offsets. “This is a real estate strategy with a decarbonization goal,” said Joseph Sumberg, the head of Galvanize Real Estate, who joined Galvanize last October from Goldman Sachs.