Utilize the input text as a context reference, choose the right relationship between Richard Tol and University of Sussex from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Richard Tol of the University of Sussex points out that homes and offices in cold countries are built to conserve heat, with large south-facing windows.

Answer: employer