"They are seeking to understand both the physical risks associated with climate change as well as the ways that climate policy will impact prices, costs and demand", Fink said.
"Every government, company, and shareholder must confront climate change", Fink continued.
Fink said BlackRock intends to make sustainable investing more accessible to all investors and lower the hurdles for those who want to act.
BlackRock now manages $50bn in funds and other products that support the transition to a low-carbon economy, including a renewable power infrastructure business, which invests in the private markets in wind and solar power, green bond funds as well as other areas.
These include ensuring that all its portfolio managers are accountable for managing exposure to environmental, social and governance (ESG) risks by the end of 2020.
In his letter, Fink stated: "Thermal coal is significantly carbon intensive, becoming less and less economically viable, and highly exposed to regulation because of its environmental impacts".
The New York company is taking immediate action and leaving investments in coal used to generate electricity, and it will start asking customers to disclose their climate-related risks. "As a result, we are in the process of removing from our discretionary active investment portfolios the public securities of companies that generate more than 25% of their revenues from thermal coal production".
He revealed that it is the top issue that clients invariably raise with BlackRock, and that this is driving a "profound reassessment of risk" and asset values worldwide.