A recent study published in Nature reveals the significant role of oceans in cooling the planet through the emission of short-lived halogens. In addition to their well-known contribution to carbon dioxide absorption and climate regulation, these halogens, including chlorine, bromine, and iodine, play a crucial role in maintaining Earth’s temperature balance. The study projects a potential increase in their cooling effect from 8-10% to 18-31% by the year 2100, emphasizing the importance of considering these factors in future climate models.
Understanding the Impact of Short-Lived Halogens:
- Lifespan and Amplification: Short-lived halogens, naturally occurring in the oceans, have a lifespan of less than six months in the atmosphere. While they have always been present, human activities have amplified their release. Pollutants, such as ozone, deposit on the ocean’s surface, converting soluble halogens into insoluble forms and causing their release into the atmosphere.
- Ozone Depletion and Warming: Halogens cause a depletion of ozone in the troposphere, a greenhouse gas that traps outgoing radiation and contributes to warming. The study found that short-lived halogens from oceans contribute to a cooling effect of -0.24 0.02 Watts per square meter (W m?2) by depleting ozone. However, their impact on methane, another greenhouse gas, is opposite. Halogens destroy hydroxyl radicals (OH), which break down methane. This results in a warming effect of 0.09 0.01 W m?2 due to the increased atmospheric lifetime of methane.
- Influence on Water Vapor and Aerosols: Short-lived halogens also affect water vapor levels in the atmosphere, leading to a warming effect of 0.011 0.001 W m?2. Moreover, they reduce the formation of cooling aerosols, which reflect sunlight. This reduction causes a small warming effect of 0.03 0.01 W m?2. Despite their warming impact on methane, water vapor, and aerosols, halogens compensate for this by destroying ozone, exerting a net cooling effect of -0.13 0.03 W m?2.
Increase in Cooling Effect:
The study projects a potential increase in the cooling effect of short-lived halogens from the current 8-10% to 18-31% by the year 2100. These findings emphasize the need to incorporate halogens into future climate models, as their contribution to the overall cooling effect cannot be overlooked. The researchers attribute the observed spike of 61% in cooling by chlorine, bromine, and iodine since the preindustrial era to the anthropogenic amplification of natural halogen emissions.
