scholarly journals FAIR v1.1: A simple emissions-based impulse response and carbon cycle model

2017 ◽  
Author(s):  
Christopher J. Smith ◽  
Piers M. Forster ◽  
Myles Allen ◽  
Nicholas Leach ◽  
Richard J. Millar ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Temperature Change ◽  
Radiative Forcing ◽  
Climate Model ◽  
Future Climate Change ◽  
Climate Response ◽  
Rcp Scenarios ◽  
Transient Climate Response ◽  
Surface Temperature Change ◽  
Future Projections

Abstract. Simple climate models can be valuable if they are able to replicate aspects of complex fully coupled earth system models. Larger ensembles can be produced, enabling a probabilistic view of future climate change. A simple emissions-based climate model, FAIR, is presented which calculates atmospheric concentrations of greenhouse gases and effective radiative forcing (ERF) from greenhouse gases, aerosols, ozone precursors and other agents. The ERFs are integrated into global mean surface temperature change. Model runs are constrained to observed temperature change from 1880 to 2016 and produce a range of future projections under the Representative Concentration Pathway (RCP) scenarios. For the historical period the ERF time series in FAIR emulates the results in the IPCC Fifth Assessment Report (AR5), whereas for RCP historical and future scenarios, the greenhouse gas concentrations in FAIR closely track the observations and projections in the RCPs. The constrained estimates of equilibrium climate sensitivity (ECS) of 2.79 (1.97 to 4.08) K, transient climate response (TCR) of 1.47 (1.03 to 2.23) K and transient climate response to cumulative CO2 emissions (TCRE) of 1.43 (1.01 to 2.16) K (1000 GtC)−1 (median and 5–95 % credible intervals) are in good agreement, with tighter uncertainty bounds, than AR5 (1.5 to 4.5 K, 1.0 to 2.5 K, and 0.8 to 2.5 K respectively). The ranges of future projections of temperature and ranges of estimates of ECS, TCR and TCRE are moderately sensitive to the historical temperature dataset used to constrain, prior distributions of ECS/TCR parameters, aerosol radiative forcing relationship and ERF from a doubling of CO2. Taking these sensitivities into account, there is no evidence to suggest that the median and credible range of observationally constrained TCR or ECS differ from climate model-derived estimates. However, the range of temperature projections under the RCP scenarios for 2081–2100 in the constrained FAIR model ensemble are lower than the emissions-based estimates reported in AR5.

scholarly journals FAIR v1.3: a simple emissions-based impulse response and carbon cycle model

2018 ◽  
Vol 11 (6) ◽  
pp. 2273-2297 ◽  
Author(s):  
Christopher J. Smith ◽  
Piers M. Forster ◽  
Myles Allen ◽  
Nicholas Leach ◽  
Richard J. Millar ◽  
...  
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Radiative Forcing ◽  
Climate Models ◽  
Climate Model ◽  
Future Climate Change ◽  
Climate Response ◽  
Transient Climate Response ◽  
Carbon Cycle Model ◽  
Future Projections

Abstract. Simple climate models can be valuable if they are able to replicate aspects of complex fully coupled earth system models. Larger ensembles can be produced, enabling a probabilistic view of future climate change. A simple emissions-based climate model, FAIR, is presented, which calculates atmospheric concentrations of greenhouse gases and effective radiative forcing (ERF) from greenhouse gases, aerosols, ozone and other agents. Model runs are constrained to observed temperature change from 1880 to 2016 and produce a range of future projections under the Representative Concentration Pathway (RCP) scenarios. The constrained estimates of equilibrium climate sensitivity (ECS), transient climate response (TCR) and transient climate response to cumulative CO2 emissions (TCRE) are 2.86 (2.01 to 4.22) K, 1.53 (1.05 to 2.41) K and 1.40 (0.96 to 2.23) K (1000 GtC)−1 (median and 5–95 % credible intervals). These are in good agreement with the likely Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) range, noting that AR5 estimates were derived from a combination of climate models, observations and expert judgement. The ranges of future projections of temperature and ranges of estimates of ECS, TCR and TCRE are somewhat sensitive to the prior distributions of ECS∕TCR parameters but less sensitive to the ERF from a doubling of CO2 or the observational temperature dataset used to constrain the ensemble. Taking these sensitivities into account, there is no evidence to suggest that the median and credible range of observationally constrained TCR or ECS differ from climate model-derived estimates. The range of temperature projections under RCP8.5 for 2081–2100 in the constrained FAIR model ensemble is lower than the emissions-based estimate reported in AR5 by half a degree, owing to differences in forcing assumptions and ECS∕TCR distributions.

Large ensemble assessment of how the global surface warming response to cumulative carbon differs for negative and positive carbon emissions  

2021 ◽  
Author(s):  
Negar Vakilifard ◽  
Katherine Turner ◽  
Ric Williams ◽  
Philip Holden ◽  
Neil Edwards ◽  
...  
Keyword(s):  
Carbon Emissions ◽  
Radiative Forcing ◽  
Climate Model ◽  
Climate Feedback ◽  
Climate Response ◽  
Ocean Heat Uptake ◽  
Transient Climate Response ◽  
Surface Warming ◽  
Radiative Processes ◽  
Negative Emission

<p>The controls of the effective transient climate response (TCRE), defined in terms of the dependence of surface warming since the pre-industrial to the cumulative carbon emission, is explained in terms of climate model experiments for a scenario including positive emissions and then negative emission over a period of 400 years. We employ a pre-calibrated ensemble of GENIE, grid-enabled integrated Earth system model, consisting of 86 members to determine the process of controlling TCRE in both CO<sub>2</sub> emissions and drawdown phases. Our results are based on the GENIE simulations with historical forcing from AD 850 including land use change, and the future forcing defined by CO<sub>2</sub> emissions and a non-CO<sub>2</sub> radiative forcing timeseries. We present the results for the point-source carbon capture and storage (CCS) scenario as a negative emission scenario, following the medium representative concentration pathway (RCP4.5), assuming that the rate of emission drawdown is 2 PgC/yr CO<sub>2</sub> for the duration of 100 years. The climate response differs between the periods of positive and negative carbon emissions with a greater ensemble spread during the negative carbon emissions. The controls of the spread in ensemble responses are explained in terms of a combination of thermal processes (involving ocean heat uptake and physical climate feedback), radiative processes (saturation in radiative forcing from CO<sub>2</sub> and non-CO<sub>2</sub> contributions) and carbon dependences (involving terrestrial and ocean carbon uptake).  </p>

scholarly journals Comparison of Climate Response to Anthropogenic Aerosol versus Greenhouse Gas Forcing: Distinct Patterns

2016 ◽  
Vol 29 (14) ◽  
pp. 5175-5188 ◽  
Author(s):  
Hai Wang ◽  
Shang-Ping Xie ◽  
Qinyu Liu
Keyword(s):  
Northern Hemisphere ◽  
Radiative Forcing ◽  
Climate Model ◽  
East Asian Monsoon ◽  
Climate Response ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Asian Monsoon Region ◽  
Surface Temperature Change ◽  
Aerosol Forcing

Abstract Spatial patterns of climate response to changes in anthropogenic aerosols and well-mixed greenhouse gases (GHGs) are investigated using climate model simulations for the twentieth century. The climate response shows both similarities and differences in spatial pattern between aerosol and GHG runs. Common climate response between aerosol and GHG runs tends to be symmetric about the equator. This work focuses on the distinctive patterns that are unique to the anthropogenic aerosol forcing. The tropospheric cooling induced by anthropogenic aerosols is locally enhanced in the midlatitude Northern Hemisphere with a deep vertical structure around 40°N, anchoring a westerly acceleration in thermal wind balance. The aerosol-induced negative radiative forcing in the Northern Hemisphere requires a cross-equatorial Hadley circulation to compensate interhemispheric energy imbalance in the atmosphere. Associated with a southward shift of the intertropical convergence zone, this interhemispheric asymmetric mode is unique to aerosol forcing and absent in GHG runs. Comparison of key climate response pattern indices indicates that the aerosol forcing dominates the interhemispheric asymmetric climate response in historical all-forcing simulations, as well as regional precipitation change such as the drying trend over the East Asian monsoon region. While GHG forcing dominates global mean surface temperature change, its effect is on par with and often opposes the aerosol effect on precipitation, making it difficult to detect anthropogenic change in rainfall from historical observations.

The Uncertainty in the Transient Climate Response to Cumulative CO2 Emissions Arising from the Uncertainty in Physical Climate Parameters

2017 ◽  
Vol 30 (2) ◽  
pp. 813-827 ◽  
Author(s):  
Andrew H. MacDougall ◽  
Neil C. Swart ◽  
Reto Knutti
Keyword(s):  
Carbon Cycle ◽  
Temperature Change ◽  
Climate Model ◽  
Transient Temperature ◽  
Climate Response ◽  
Earth System ◽  
Intergovernmental Panel ◽  
Transient Climate Response ◽  
Total Uncertainty ◽  
Near Surface

An emergent property of most Earth system models is a near-linear relationship between cumulative emission of CO2 and change in global near-surface temperature. This relationship, which has been named the transient climate response to cumulative CO2 emissions (TCRE), implies a finite budget of fossil fuel carbon that can be burnt over all time consistent with a chosen temperature change target. Carbon budgets are inversely proportional to the value of TCRE and are therefore sensitive to the uncertainty in TCRE. Here the authors have used a perturbed physics approach with an Earth system model of intermediate complexity to assess the uncertainty in the TCRE that arises from uncertainty in the rate of transient temperature change and the effect of this uncertainty on carbon cycle feedbacks. The experiments are conducted using an idealized 1% yr−1 increase in CO2 concentration. Additionally, the authors have emulated the temperature output of 23 models from phase 5 of the Climate Model Intercomparison Project (CMIP5). The experiment yields a mean value for TCRE of 1.72 K EgC−1 with a 5th to 95th percentile range of 0.88 to 2.52 K EgC−1. This range of uncertainty is consistent with the likely range from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (0.8 to 2.5 K EgC−1) but by construction underestimates the total uncertainty range of TCRE, as the authors’ experiments cannot account for the uncertainty from their models’ imperfect representation of the global carbon cycle. Transient temperature change uncertainty induces a 5th to 95th percentile range in the airborne fraction at the time of doubled atmospheric CO2 of 0.50 to 0.58. Overall the uncertainty in the value of TCRE remains considerable.

scholarly journals How Much Human-Caused Global Warming Should We Expect with Business-As-Usual (BAU) Climate Policies? A Semi-Empirical Assessment

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1365 ◽  
Author(s):  
Ronan Connolly ◽  
Michael Connolly ◽  
Robert M. Carter ◽  
Willie Soon
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Greenhouse Gases ◽  
Climate Sensitivity ◽  
Climate Model ◽  
Global Climate Model ◽  
Future Climate Change ◽  
Transient Climate Response ◽  
Semi Empirical ◽  
Business As Usual

In order to assess the merits of national climate change mitigation policies, it is important to have a reasonable benchmark for how much human-caused global warming would occur over the coming century with “Business-As-Usual” (BAU) conditions. However, currently, policymakers are limited to making assessments by comparing the Global Climate Model (GCM) projections of future climate change under various different “scenarios”, none of which are explicitly defined as BAU. Moreover, all of these estimates are ab initio computer model projections, and policymakers do not currently have equivalent empirically derived estimates for comparison. Therefore, estimates of the total future human-caused global warming from the three main greenhouse gases of concern (CO2, CH4, and N2O) up to 2100 are here derived for BAU conditions. A semi-empirical approach is used that allows direct comparisons between GCM-based estimates and empirically derived estimates. If the climate sensitivity to greenhouse gases implies a Transient Climate Response (TCR) of ≥ 2.5 °C or an Equilibrium Climate Sensitivity (ECS) of ≥ 5.0 °C then the 2015 Paris Agreement’s target of keeping human-caused global warming below 2.0 °C will have been broken by the middle of the century under BAU. However, for a TCR < 1.5 °C or ECS < 2.0 °C, the target would not be broken under BAU until the 22nd century or later. Therefore, the current Intergovernmental Panel on Climate Change (IPCC) “likely” range estimates for TCR of 1.0 to 2.5 °C and ECS of 1.5 to 4.5 °C have not yet established if human-caused global warming is a 21st century problem.

scholarly journals The Sensitivity of the Proportionality between Temperature Change and Cumulative CO2 Emissions to Ocean Mixing

2017 ◽  
Vol 30 (8) ◽  
pp. 2921-2935 ◽  
Author(s):  
Dana Ehlert ◽  
Kirsten Zickfeld ◽  
Michael Eby ◽  
Nathan Gillett
Keyword(s):  
Temperature Change ◽  
Temperature Sensitivity ◽  
Radiative Forcing ◽  
Climate Model ◽  
Surface Air Temperature ◽  
Carbon Fluxes ◽  
Ocean Mixing ◽  
Mixing Processes ◽  
Transient Climate Response ◽  
Over Time

The ratio of global mean surface air temperature change to cumulative CO2 emissions, referred to as transient climate response to cumulative CO2 emissions (TCRE), has been shown to be approximately constant on centennial time scales. The mechanisms behind this constancy are not well understood, but previous studies suggest that compensating effects of ocean heat and carbon fluxes, which are governed by the same ocean mixing processes, could be one cause for this approximate constancy. This hypothesis is investigated by forcing different versions of the University of Victoria Earth System Climate Model, which differ in the ocean mixing parameterization, with an idealized scenario of 1% annually increasing atmospheric CO2 until quadrupling of the preindustrial CO2 concentration and constant concentration thereafter. The relationship between surface air warming and cumulative emissions remains close to linear, but the TCRE varies between model versions, spanning the range of 1.2°–2.1°C EgC−1 at the time of CO2 doubling. For all model versions, the TCRE is not constant over time while atmospheric CO2 concentrations increase. It is constant after atmospheric CO2 stabilizes at 1120 ppm, because of compensating changes in temperature sensitivity (temperature change per unit radiative forcing) and cumulative airborne fraction. The TCRE remains approximately constant over time even if temperature sensitivity, determined by ocean heat flux, and cumulative airborne fraction, determined by ocean carbon flux, are taken from different model versions with different ocean mixing settings. This can partially be explained with temperature sensitivity and cumulative airborne fraction following similar trajectories, which suggests ocean heat and carbon fluxes scale approximately linearly with changes in vertical mixing.

scholarly journals Rates of global temperature change during the past millennium

2011 ◽  
Vol 7 (4) ◽  
pp. 2341-2354
Author(s):  
C. Shen ◽  
W.-C. Wang ◽  
G. Zeng ◽  
Y. Peng ◽  
Y. Xu
Keyword(s):  
Greenhouse Gases ◽  
Surface Temperature ◽  
Temperature Change ◽  
20Th Century ◽  
Time Scale ◽  
Climate Model ◽  
Global Climate Model ◽  
Surface Temperature Change ◽  
The Past ◽  
Past Millennium

Abstract. We examine the characteristics (amplitude and phase) of the temporal variation in the rates of global-mean surface temperature change during the past millennium. The study was conducted by applying 20-, 30-, and 50-yr sliding windows to the observations of recent century and reconstructions of earlier times. The analysis focuses on the characteristics of the 20th century within the context of the millennium as well as their sensitivity to the low frequency variability of sea surface temperature (SST) and time scales. On 20-yr time scale, comparable rates to that of the 20th century in both amplitude and phase occur in earlier nine centuries. The peak in the amplitude of rates in the 20th century on 30-yr time scale, although is not the largest during the past millennium, but is the most persistent. On 50-yr time scale, the 20th century warming rates are the highest and the most persistent during the past millennium. The results also indicate that although the SST variability does not affect much the amplitude of the rates, but the phases is quite different, thus highlighting the importance of the role of oceans in affecting the rates. We also analyzed the characteristics from global climate model (1000–1999 AD) simulations with different climate (solar, volcanic, and greenhouse gases) forcing. Except for the one driven by the solar forcing, other forcing simulates similar amplitudes as the observed ones. However, only greenhouse gases (GHG) forcing can reproduce the persistent high warming rates of the 20th century.

Quantifying the probability distribution function of the Transient Climate Response to Cumulative CO2 Emissions

2020 ◽  
Author(s):  
Lynsay Spafford ◽  
Andrew MacDougall
Keyword(s):  
Temperature Change ◽  
Radiative Forcing ◽  
Carbon Budget ◽  
Fold Increase ◽  
Climate Feedback ◽  
Transient Climate Response ◽  
Surface Temperature Change ◽  
Log Normal ◽  
Log Normal Distribution ◽  
Global Surface

&lt;p&gt;The Transient Climate Response to Cumulative CO&lt;sub&gt;2&lt;/sub&gt; Emissions (TCRE) is the proportionality between global temperature change and cumulative CO&lt;sub&gt;2&lt;/sub&gt; emissions. The TCRE implies a finite quantity of CO&lt;sub&gt;2&lt;/sub&gt; emissions, or carbon budget, consistent with a given temperature change limit. The uncertainty of the TCRE is often assumed be normally distributed, but this assumption has yet to be validated. We calculated the TCRE using a zero-dimensional ocean diffusive model and a Monte-Carlo error propagation (n=10 000 000) randomly drawing from probability density functions of the climate feedback parameter, the land-borne fraction of carbon, effective ocean diffusivity, radiative forcing from an e-fold increase in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration, and the ratio of sea to global surface temperature change. The calculated TCRE has a positively skewed distribution, ranging from 1.1-2.9 K EgC&lt;sup&gt;-1&lt;/sup&gt; (5-95% confidence), with a mean and median value of 1.9 K EgC&lt;sup&gt;-1&lt;/sup&gt; and 1.8 K EgC&lt;sup&gt;-1&lt;/sup&gt;. The calculated distribution of the TCRE is well described by a log-normal distribution. The CO&lt;sub&gt;2&lt;/sub&gt;-only carbon budget compatible with 2&amp;#176;C warming is 1 100 PgC, ranging from 700-1 800 PgC (5-95% confidence) estimated using a simplified model of ocean dynamics. Climate sensitivity (climate feedback) is the most influential Earth system parameter on the TCRE, followed by the land-borne fraction of carbon, radiative forcing from an e-fold increase in CO&lt;sub&gt;2&lt;/sub&gt;, effective ocean diffusivity, and the ratio of sea to global surface temperature change. While the uncertainty of the TCRE is considerable, the use of a log-normal distribution may improve estimations of the TCRE and associated carbon budgets.&lt;/p&gt;

scholarly journals The Norwegian Earth System Model, NorESM1-M – Part 2: Climate response and scenario projections

2012 ◽  
Vol 5 (3) ◽  
pp. 2933-2998 ◽  
Author(s):  
T. Iversen ◽  
M. Bentsen ◽  
I. Bethke ◽  
J. B. Debernard ◽  
A. Kirkevåg ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Ocean Model ◽  
Climate Response ◽  
Rcp Scenarios ◽  
Transient Climate Response ◽  
Near Surface ◽  
Enso Events ◽  
Model Average

Abstract. The NorESM1-M simulation results for CMIP5 (http://cmip-pcmdi.llnl.gov/cmip5/index.html) are described and discussed. Together with the accompanying paper by Bentsen et al. (2012), this paper documents that NorESM1-M is a valuable global climate model for research and for providing complementary results to the evaluation of possible man made climate change. NorESM is based on the model CCSM4 operated at NCAR on behalf of many contributors in USA. The ocean model is replaced by a developed version of MICOM and the atmospheric model is extended with on-line calculations of aerosols, their direct effect, and their indirect effect on warm clouds. Model validation is presented in a companion paper (Bentsen et al., 2012). NorESM1-M is estimated to have equilibrium climate sensitivity slightly smaller than 2.9 K, a transient climate response just below 1.4 K, and is less sensitive than most other models. Cloud feedbacks damp the response, and a strong AMOC reduces the heat fraction available for increasing near surface temperatures, for evaporation, and for melting ice. The future projections based on RCP scenarios yield global surface air temperature increase almost one standard deviation lower than a 15-model average. Summer sea-ice is projected to decrease considerably by 2100, and completely for RCP8.5. The AMOC is projected to reduce by 12%, 15–17%, and 32% for the RCP2.6, 4.5, 6.0 and 8.5 respectively. Precipitation is projected to increase in the tropics, decrease in the subtropics and in southern parts of the northern extra-tropics during summer, and otherwise increase in most of the extra-tropics. Changes in the atmospheric water cycle indicate that precipitation events over continents will become more intense and dry spells more frequent. Extra-tropical storminess in the Northern Hemisphere is projected to shift northwards. There are indications of more frequent spring and summer blocking in the Euro-Atlantic sectors and that ENSO events weaken but appear more frequent. These indications are uncertain because of biases in the model's representation of present-day conditions. There are indications that positive phase PNA and negative phase NAO become less frequent under the RCP8.5 scenario, but also this result is considered uncertain. Single-forcing experiments indicate that aerosols and greenhouse gases produce similar geographical patterns of response for near surface temperature and precipitation. These patterns tend to have opposite sign, with important exceptions for precipitation at low latitudes. The asymmetric aerosol effects between the two hemispheres leads to a southward displacement of ITCZ. Both forcing agents thus tend to reduce northern hemispheric subtropical precipitation.

Sign in / Sign up

Export Citation Format

Share Document