Most of us have heard of carbon offsets. Perhaps a relative mentioned that she buys them when she books airplane tickets. Or maybe you have read how huge corporations like Microsoft purchase offsets to reduce their carbon footprints. Lately, carbon offsets have generated much debate. What is the hullabaloo all about?

Carbon emissions trading, often known as the carbon market, seeks to limit climate change by putting a price on the emission of greenhouse gases like carbon dioxide. Individuals and companies who buy carbon offset certificates are investing in reforestation, renewable energy development, and other projects intended to reduce carbon emissions. Purchasing a certificate thus compensates for — or offsets — the investor’s release of a certain amount of carbon dioxide (or the equivalent in greenhouse gases).

In this country, excepting a few states with mandatory cap-and-trade systems (to be covered in a future column), the purchase of carbon offsets is entirely voluntary. Accordingly, American citizens and companies are knowingly making investments from which they will realize no direct financial return. Individuals who adopt this unconventional investment style seek to mitigate emissions-driven climate change. Some companies purchase carbon offsets for the same reason, but more typically their investments are driven by pressure from eco-conscious consumers.

Political attacks aside, criticism of the carbon offset sector derives from several concerns, beginning with its opaqueness. Various organizations, including the US government and the Integrity Council for the Voluntary Carbon Market, have published different statements of market principles, while a whole host of carbon registries, such as Verra and Gold Standard, score projects according to their own methodologies. This lack of uniformity hinders independent analysis of market efficacy.

Another issue is that some purchases are suspect. These include offsets sold in connection with projects which would have been built regardless, such as hydroelectric dams in the Amazon and wind farms throughout India. Also, carbon offsets may actually delay the vital transition away from fossil fuels by suggesting that burning them at current levels is sustainable. However, with climate change accelerating, we can no longer seek to have our cake and eat it too. Let’s stop fooling ourselves and get right to the hard work of changing our behavior.

David Conwell is a former history teacher who belongs to Brunswick’s Sustainability Committee and the nationwide advocacy organization Citizens’ Climate Lobby.