Phytoplankton Climate Regulation in Positive and Negative Feedback Systems: The CLAW and anti-CLAW hypotheses

Adam Stoer \ Oceans First, Issue 4, 2017, pgs. 43-52.  Download PDF


The global climate crisis is bigger now than it has ever been before, pushing for much-needed research on the consequences of climate change. In 1987, Charlson, Lovelock, Andreae, and Warren proposed the CLAW hypothesis which stated that phytoplankton contribute to the production of a significant amount of cloud condensation nuclei (CCN) which in turn creates a negative feedback loop after there is an initial temperature rise. Many years later, in 2006, Lovelock proposed the anti-CLAW hypothesis, which argues that a similar process occurs except that it works as a positive feedback system. Both hypotheses have created much controversy about the effects phytoplankton has on climate and climate regulation. Research has shown that different types of phytoplankton tend to have higher growth rates within a temperature range. Coccolithophores are known for their contribution of DMSP, a compound that forms to make CCN as well as their carbon sequestration abilities. This type of phytoplankton typically function at a thermal niche where nutrient stratification is not strongly limiting, making them act like a buffer against further temperature rises in terms of the CLAW hypothesis. Based on the physiological capabilities of phytoplankton within their environment, both the CLAW and anti-CLAW mechanisms correlate strongly with coccolithophorid algae.