Contrasting futures for ocean and society from different anthropogenic CO ₂ emissions scenarios

Abstract

The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystems—and the goods and services they provide—for growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenario—consistent with the Copenhagen Accord's goal of a global temperature increase of less than 2°C—is much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new climate regime that fails to minimize ocean impacts would be incomplete and inadequate.

Interactive network configuration maintains bacterioplankton community structure under elevated CO<sub>2</sub> in a eutrophic coastal mesocosm experiment

“…Consequently, it is predicted that under a "business-as-usual" CO 2 emission scenario, the present average surface pH value will drop 0.4 units over the next century (Gattuso et al, 2015). Despite a growing interest in the importance of the roles of marine bacterioplankton in ocean ecosystems and biogeochemical cycles, our current understanding of their responses to ocean acidification is still limited.…”

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

“…these two diagnostics because they are associated with different biological impacts and are not necessarily well correlated . In the future, the global mean changes in pH and aragonite saturation state will be proportional to the emissions trajectories following Gattuso et al (2015), with the largest changes associated with the higher emissions (RCP8.5) (Fig. 2c-d).…”

“…Potential impacts include changes in calcification, fecundity, organism growth and physiology, species composition and distributions, food web structure, and nutrient availability (Doney et al, 2012;Fabry et al, 2008;Iglesias-Rodriguez et al, 2008;Munday et al, 2009Munday et al, , 2010. Within this century, the impacts of ocean acidification will increase in proportion to emissions (Gattuso et al, 2015). Furthermore, these changes will be long-lasting, persisting for centuries or longer even if emissions are halted (Frolicher and Joos, 2010).…”

Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity

“…The ongoing oceanic absorption of atmospheric CO 2 has helped to restrict present global warming by reducing the total amount of manmade CO 2 in the atmosphere. However, this massive oceanic uptake of CO 2 (28% of anthropogenic CO 2 emissions since the 1970s) has altered carbonate chemistry cycles in the global ocean, disturbing its delicate geochemical balance 4 . This disruption of carbonate chemistry processes, known collectively as ocean acidification, has been of great scientific interest and of growing public concern 5 .…”