English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

. The sixth phase of the Coupled Model Intercomparison Project (CMIP6) is thelatest modeling effort for general circulation models to simulate andproject various aspects of climate change. Many of the general circulationmodels (GCMs) participating in CMIP6 provide archived output that can beused to calculate effective climate sensitivity (ECS) and forecast futuretemperature change based on emissions scenarios from several SharedSocioeconomic Pathways (SSPs). Here we use our multiple linear regressionenergy balance model, the Empirical Model of Global Climate (EM-GC), tosimulate and project changes in global mean surface temperature (GMST),calculate ECS, and compare to results from the CMIP6 multi-model ensemble.An important aspect of our study is a comprehensive analysis of uncertaintiesdue to radiative forcing of climate from tropospheric aerosols (AER RF) inthe EM-GC framework. We quantify the attributable anthropogenic warming rate(AAWR) from the climate record using the EM-GC and use AAWR as a metric todetermine how well CMIP6 GCMs replicate human-driven global warming over thelast 40 years. The CMIP6 multi-model ensemble indicates a median value ofAAWR over 1975–2014 of 0.221 ∘C per decade (range of 0.151 to0.299 ∘C per decade; all ranges given here are for 5th and95th confidence intervals), which is notably faster warming than ourmedian estimate for AAWR of 0.157 ∘C per decade (range of 0.120to 0.195 ∘C per decade) inferred from the analysis of the HadleyCentre Climatic Research Unit version 5 data record for GMST. Estimates ofECS found using the EM-GC assuming that climate feedback does not vary over time(best estimate 2.33 ∘C; range of 1.40 to 3.57 ∘C) aregenerally consistent with the range of ECS of 1.5 to 4.5 ∘C givenby the IPCC's Fifth Assessment Report. The CMIP6 multi-model ensemble exhibitsconsiderably larger values of ECS (median 3.74 ∘C; range of 2.19to 5.65 ∘C). Our best estimate of ECS increases to 3.08 ∘C (range of 2.23 to 5.53 ∘C) if we allow climate feedback to varyover time. The dominant factor in the uncertainty for our empiricaldeterminations of AAWR and ECS is imprecise knowledge of AER RF for thecontemporary atmosphere, though the uncertainty due to time-dependentclimate feedback is also important for estimates of ECS. We calculate thelikelihood of achieving the Paris Agreement target (1.5 ∘C) andupper limit (2.0 ∘C) of global warming relative to pre-industrialfor seven of the SSPs using both the EM-GC and the CMIP6 multi-modelensemble. In our model framework, SSP1-2.6 has a 53 % probability oflimiting warming at or below the Paris target by the end of the century, andSSP4-3.4 has a 64 % probability of achieving the Paris upper limit. Theseestimates are based on the assumptions that climate feedback has been andwill remain constant over time since the prior temperature record can be fitso well assuming constant climate feedback. In addition, we quantify thesensitivity of future warming to the curbing of the current rapid growth ofatmospheric methane and show that major near-term limits on the future growth ofmethane are especially important for achievement of the 1.5 ∘Cgoal of future warming. We also quantify warming scenarios assuming climatefeedback will rise over time, a feature common among many CMIP6 GCMs; underthis assumption, it becomes more difficult to achieve any specific warmingtarget. Finally, we assess warming projections in terms of futureanthropogenic emissions of atmospheric carbon. In our model framework,humans can emit only another 150±79 Gt C after 2019 to have a 66 %likelihood of limiting warming to 1.5 ∘C and another 400±104 Gt C to have the same probability of limiting warming to 2.0 ∘C. Given the estimated emission of 11.7 Gt C per year for 2019 due tocombustion of fossil fuels and deforestation, our EM-GC simulations suggestthat the 1.5 ∘C warming target of the Paris Agreement will not beachieved unless carbon and methane emissions are severely curtailed in thenext 10 years.

Comparison of CMIP6 historical climate simulations and future projected warming to an empirical model of global climate