Status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.
Accounting for multiple forcing factors and product substitution enforces the cooling effect of boreal forests
Eero Nikinmaa1,†,Tuomo Kalliokoski1,2,Kari Minkkinen1,Jaana Bäck1,Michael Boy2,Yao Gao3,Nina Janasik-Honkela4,Janne I. Hukkinen4,Maarit Kallio5,Markku Kulmala2,Nea Kuusinen1,Annikki Mäkelä1,Brent D. Matthies1,Mikko Peltoniemi5,Risto Sievänen5,Ditte Taipale1,2,7,Lauri Valsta1,Anni Vanhatalo1,Martin Welp6,Luxi Zhou2,Putian Zhou2,and Frank Berninger1Eero Nikinmaa et al.Eero Nikinmaa1,†,Tuomo Kalliokoski1,2,Kari Minkkinen1,Jaana Bäck1,Michael Boy2,Yao Gao3,Nina Janasik-Honkela4,Janne I. Hukkinen4,Maarit Kallio5,Markku Kulmala2,Nea Kuusinen1,Annikki Mäkelä1,Brent D. Matthies1,Mikko Peltoniemi5,Risto Sievänen5,Ditte Taipale1,2,7,Lauri Valsta1,Anni Vanhatalo1,Martin Welp6,Luxi Zhou2,Putian Zhou2,and Frank Berninger1
Received: 13 Apr 2017 – Discussion started: 12 May 2017
Abstract. There is dispute over the climate change mitigating effect of boreal forest management due to the contrasting influence it has on different vectors influencing radiative forcing (RF). For the first time, this study has combined the estimated effects of carbon sequestration in forests and wood products, the surface albedo of forests, the direct and indirect forcing of secondary organic aerosols and the avoidance of fossil emissions by product substitution, both in the current and predicted 2050 climate. The aerosol effect was comparable in magnitude to that of carbon sequestration and increased in importance in a warmer 2050 climate. Harvesting decreased the formation of climate cooling aerosols. The aerosol effect was also larger than the opposing impact of increased surface albedo due to clear cutting in conifer forests. When all above mentioned RF factors were accounted for, the RF of conifer-dominated stands was less negative than that of broadleaf-dominated stands, despite the higher carbon sequestration of the former. Considering also the cooling effect of product substitution, the differences in the RF impact of management alternatives that maintained or increased forest biomass were small. However, the outcome depended heavily on the wood use pattern and the assumed product substitution. A substantial increase in harvest with a clear increase in the share of small dimension fiber and fuel wood use led to a clear climate warming effect in the simulations.
We estimated the impact of boreal forest management on climate, considering the effects of carbon, albedo, aerosols, and effects of industrial wood use. We made analyses both in current and warmer climate of 2050. The aerosol effect was comparable to that of carbon sequestration. Deciduous trees may have a large potential for mitigation due to their high albedo and aerosol effects. If the forests will be used more intensively and mainly for pulp and energy, the warming influence is clear.
We estimated the impact of boreal forest management on climate, considering the effects of...