Climate change is the topic of the day. The World Meteorological Organization tells us that the 2011-20 decade was the warmest on record. Earlier this year, the U.S. government re-joined the Paris Accord, and is proposing a range of new programs to mitigate the long-run impact of climate change. Now that a warming planet has made the Arctic increasingly navigable, national security specialists are concerned about geopolitical risks there. Thousands of economists have endorsed a carbon tax. Even central banks have joined together to form the Network for the Greening of the Financial System—a forum to discuss how to take account of climate change in assessing financial stability.
Against that background, last month, NYU Stern’s Volatility and Risk Institute (VRI) held a conference on finance and climate change. Speakers addressed issues ranging from the modeling and measurement of climate risk in finance to assessing its impact on the resilience of the financial system. In this post, we primarily focus on one of the central challenges facing policymakers and practitioners: what is the appropriate discount rate for evaluating the relative costs and benefits of investments in climate change mitigation that will not pay off for decades? We also comment briefly on several other issues in the rapidly growing field of climate finance research.
Past responses to the discount-rate question vary widely. Some observers call for a discount rate matching the high expected return on long-lived, risky assets—a number as high as 7%. This would imply a very low present value of benefits from investments to mitigate climate change, consistent with only modest current expenditures. Others postulate that climate change could lead to the extinction of humanity. For plausible discount rates, the specter of a nearly infinite loss means that virtually any level of mitigation investment is warranted (see, for example, Holt).
Recent climate finance research that we summarize here comes to the conclusion that over any reasonable horizon, the appropriate discount rate for computing the net present value of investments in climate change mitigation should be relatively low….
Many people find negative interest rates confusing. Why should anyone pay a bank to make a deposit? Why should a bank pay someone to borrow? How can we value an asset with a future cash flow when the interest rate is negative?
Policymakers also wonder whether the effects of negative interest rates on the economy are favorable or unfavorable. Do negative interest rates help central banks achieve price stability by stimulating economic activity? Do negative rates spur banks to make more good loans or to evergreen bad ones? Will borrowers and banks take on too much risk because they can fund investments at a negative rate? Will households reduce their saving rate because the return is so low, or raise it because low returns leave them farther from their wealth target? Will negative rates influence the ability of pension funds, insurance companies and governments to make good on their long-term promises to future retirees?
In this primer, we examine these questions, starting with key facts about negative nominal interest rates. Our conclusion: there is little magic about having a slightly negative, as opposed to slightly positive interest rates. Thus, much of the criticism of persistently negative nominal interest rates applies similarly to very low, but positive rates. That said, financial system frictions limit the favorable impact from modestly negative nominal rates, but our experience with them remains limited. Given the likely need for unconventional policy tools to address the next recession, learning more about the benefits and costs of negative nominal interest rates is a high priority….
