6. Conclusions and discussion
The AMPERE Work Package 2 model inter-comparison
study, which engaged nine participating integrated assessment
modeling teams, explored the implications of less-than-optimal
near-term emission mitigation for mid- and long-term transition
pathways, which limit climate forcing to 450 ppm CO2e in
2100, and interactions with technology availability.
6.1. Findings
This study reaffirms two important findings. We found no
“Silver-Bullet” technology whose deployment accounted for
all emission mitigation and, thus, eliminated the need for
other emission mitigation technologies. We also found that
multiple technology transition pathway portfolios could be
used to achieve the long term goal of low climate forcing.
The long-term goal, 450 ppm CO2e, was implemented as a
cumulative net emission limit of 1500 GtCO2 between 2000
and 2100. However, no limit was set on either annual or
cumulative emissions prior to the year 2100. That is, “overshoot”
scenarios were allowed. Modeling teams reported
negative net global CO2 emissions when BECCS was available.
When BECCS was available, models used this option to exceed
the 1500 GtCO2 budget in the mid-term removing the excess
with BECCS in the long term. Excluding either bioenergy or
CCS limited the role of negative emissions and strongly shifted
emission mitigation toward the near-term. The foregone
long-term negative emission option greatly increased the risk
of failing to achieve the long-term climate goal, particularly
when combined with delayed near-term policy actions.
The study highlighted the critical importance of the
period between 2030 and 2050, in which the largest
percentage shift from emitting to non-emitting technology
occurs. Less-than-optimal emission mitigation in the period
2010 to 2030 simply increases the challenge in the
next 20 years, requiring even more rapid shifts toward
non-emitting energy technologies. We found that on
average 70% of the 1500 GtCO2 21st century emission budget
was used by the year 2030 and that the remainder of the
budget was allocated in the remaining 70 years. The absence
of a “Silver-Bullet” technology in achieving the long-term
climate goal points to the fact that a broad range of
responses will collectively make a major difference, suggesting
that global energy R&D programs need to take a
portfolio approachwith an emphasis on overall performance
of emission mitigation.
6. Conclusions and discussion
The AMPERE Work Package 2 model inter-comparison
study, which engaged nine participating integrated assessment
modeling teams, explored the implications of less-than-optimal
near-term emission mitigation for mid- and long-term transition
pathways, which limit climate forcing to 450 ppm CO2e in
2100, and interactions with technology availability.
6.1. Findings
This study reaffirms two important findings. We found no
“Silver-Bullet” technology whose deployment accounted for
all emission mitigation and, thus, eliminated the need for
other emission mitigation technologies. We also found that
multiple technology transition pathway portfolios could be
used to achieve the long term goal of low climate forcing.
The long-term goal, 450 ppm CO2e, was implemented as a
cumulative net emission limit of 1500 GtCO2 between 2000
and 2100. However, no limit was set on either annual or
cumulative emissions prior to the year 2100. That is, “overshoot”
scenarios were allowed. Modeling teams reported
negative net global CO2 emissions when BECCS was available.
When BECCS was available, models used this option to exceed
the 1500 GtCO2 budget in the mid-term removing the excess
with BECCS in the long term. Excluding either bioenergy or
CCS limited the role of negative emissions and strongly shifted
emission mitigation toward the near-term. The foregone
long-term negative emission option greatly increased the risk
of failing to achieve the long-term climate goal, particularly
when combined with delayed near-term policy actions.
The study highlighted the critical importance of the
period between 2030 and 2050, in which the largest
percentage shift from emitting to non-emitting technology
occurs. Less-than-optimal emission mitigation in the period
2010 to 2030 simply increases the challenge in the
next 20 years, requiring even more rapid shifts toward
non-emitting energy technologies. We found that on
average 70% of the 1500 GtCO2 21st century emission budget
was used by the year 2030 and that the remainder of the
budget was allocated in the remaining 70 years. The absence
of a “Silver-Bullet” technology in achieving the long-term
climate goal points to the fact that a broad range of
responses will collectively make a major difference, suggesting
that global energy R&D programs need to take a
portfolio approachwith an emphasis on overall performance
of emission mitigation.
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