Half of investors who are worried about climate change do not realize that it could affect their portfolios, says a new study by Impax Asset Management released Tuesday.

The survey of 300 investors with at least $500,000 in their portfolios shows that two-thirds are concerned about global warming as an environmental phenomenon, but only one-third know it could pose a risk to their investments.

“We found a disconnect that amazed me,” says David Richardson, managing director and global head of marketing and client services at Impax. “On the one hand, these investors are acknowledging that climate change poses a risk, but they are not recognizing that the risk of climate change is also an investment risk and is likely to impact their portfolio.”

Impax, with $4.7 billion in assets under management and advisement, primarily serves institutional clients. The company’s investments take into consideration environmental, infrastructure and population issues.

The survey revealed some contradictory actions by investors. Slightly more than half of the respondents who invest in fossil fuels are concerned about climate change, while more than 40 percent of those who say climate change poses a risk to their portfolios also hold fossil-fuel investments.

Only 38 percent of respondents who believe climate change poses a risk to their portfolio invest in assets focused on environmental solutions such as sustainability, clean energy and energy efficiency. At the same time, 46 percent of respondents who say that they are not concerned about climate change invest in assets focused on sustainability.

“This suggests that concern about climate change is not a strong determinant when it comes to informed investment decisions,” says Impax.

“Because climate change is not perceived to be an imminent threat, people don’t have any sense of urgency to act on it,” says Richardson. “That is where people are wrong. There are risks in the shorter term.” These risks include regulatory risks, such as increasing carbon taxes on carbon-heavy industries such as oil and gas, energy and transportation. Such taxes could significantly diminish the returns of companies in these industries.

“We are not suggesting that investors allocate 100 percent of their assets to energy-efficient stocks and bonds,” says Richardson. “We recommend that investors seek further information on the implications of climate change on their portfolio and begin to realize the importance of including exposure to some energy-efficient assets when investing.”