To the Editor:

Re “California Leads, Again, on Climate” (editorial, July 24):

While California’s extension of its cap-and-trade program will serve to reduce greenhouse gas emissions and stimulate a shift to cleaner fuels, this approach is not sustainable in the long term.

Levying a tariff for the right to pollute is not a mitigation strategy, nor is burning cleaner fuels. Clearly what is needed is the deployment of technology that in real time renders benign the greenhouse gas emissions from the combustion of fossil fuels.

Imagine a process that enables the burning of coal so as to emit no carbon dioxide. It’s time for bold, imaginative thinking that will lead to the needed radical innovation.

DONALD R. SADOWAY

CAMBRIDGE, MASS.

The writer is a professor of materials chemistry at M.I.T.

To the Editor:

“California Gets Emissions Cap 10 Years Longer” (news article, July 18) notes that Gov. Jerry Brown presented the state’s cap-and-trade bill as “a model for other states and nations.” Yet the bill, heavily influenced by the oil and gas industry, makes California’s flawed cap-and-trade system worse by allowing excessive allowances to pollute and prevent local regulation of greenhouse gases.