Banks' accounting of these emissions will impact their targets for becoming carbon-neutral.
The banks have also expressed concern about capital market-related emissions dwarfing their lending-related emissions, the sources said.
The Partnership for Carbon Accounting Financials (PCAF), an association of banks seeking to harmonise carbon accounting across the industry, formed the working group comprising major banks in the hope that others will follow the standard that emerges.
PCAF's board will now have the final say on whether to adopt the 33% accounting share for capital markets.
A Standard Chartered spokesperson said the bank was comfortable with any emissions accounting threshold and declined to comment further.
Persons:
Banks, Morgan Stanley, PCAF, ShareAction, Xavier Lerin, Tommy Reggiori Wilkes, Greg Roumeliotis, Rosalba O'Brien
Organizations:
Sierra Club, Carbon Accounting, Barclays, Bank of America, Citigroup, HSBC, BNP, NatWest, Standard Chartered, United Nations, Thomson
Locations:
London