Robust constraints on past CO2 climate forcing from the boron isotope proxy

The atmospheric concentration of the greenhouse gas carbon dioxide, CO2, is intimately coupled to the carbon chemistry of seawater, such that the radiative climate forcing from CO2 can be changed by an array of physical, geochemical and biological ocean processes. For instance, biological carbon sequestration, seawater cooling and net CaCO3 dissolution are commonly invoked as the primary drivers of CO2 change that amplify the orbitally‐paced ice age cycles of the late Pleistocene. Based on first‐principle arguments with regard to ocean chemistry we demonstrate that seawater pH change (∆pH) is the dominant control that effectively sets CO2 radiative forcing (∆F) on orbital timescales, as is evident from independent late Pleistocene reconstructions of pH and CO2. In short, all processes relevant for CO2 on orbital timescales, including temperature change, cause pH to change to bring about fractional CO2 change so as to yield a linear relationship of ∆pH to CO2 climate forcing. Further, we show that ∆pH and CO2 climate forcing can be reconstructed using the boron isotope pH‐proxy more accurately than absolute pH or CO2, even if seawater boron isotope composition is poorly constrained and without information on a second carbonate system parameter. Thus, our formalism relaxes otherwise necessary assumptions to allow the accurate determination of orbital timescale CO2 radiative forcing from boron isotope‐pH reconstructions alone, thereby eliminating a major limitation of current methods to estimate our planet’s climate sensitivity from the geologic record.

Hain M. P., Foster G. L. & Chalk T., 2018. Robust constraints on past CO2 climate forcing from the boron isotope proxy. Paleoceanography and Paleoclimatology. Article (subscription required).

 

0 Responses to “Robust constraints on past CO2 climate forcing from the boron isotope proxy”



  1. Leave a Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.




Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,119,142 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book