Gyrokinetic simulations of the kinetic electron effects on the electrostatic instabilities on the ITER baseline scenario

The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the International Thermonuclear Experimental Reactor(ITER)baseline scenario.The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron model and the fully drift-kinetic electron model in the NLT code,respectively.The linear simulations focus on the dependence of linear frequency on the plasma parameters,such as the ion and electron temperature gradientsκ_(Ti,e)≡R=L_(Ti,e),the density gradientκ_(n)≡R/L_(n)and the ion-electron temperature ratioτ=T_(e)=T_(i).Here,is the major radius,and T_(e)and T_(i)denote the electron and ion temperatures,respectively.L_(A)=-(δ_(r)lnA)^(-1)is the gradient scale length,with denoting the density,the ion and electron temperatures,respectively.In the kinetic electron model,the ion temperature gradient(ITG)instability and the trapped electron mode(TEM)dominate in the small and large k_(θ)region,respectively,wherek_(θ)is the poloidal wavenumber.The TEMdominant region becomes wider by increasing(decreasing)κ_(T_(e))(κ_(T_(i)))or by decreasingκ_(n).For the nominal parameters of the ITER baseline scenario,the maximum growth rate of dominant ITG instability in the kinetic electron model is about three times larger than that in the adiabatic electron model.The normalized linear frequency depends on the value ofτ,rather than the value of T_(e)or T_(i),in both the adiabatic and kinetic electron models.The nonlinear simulation results show that the ion heat diffusivity in the kinetic electron model is quite a lot larger than that in the adiabatic electron model,the radial structure is finer and the time oscillation is more rapid.In addition,the magnitude of the fluctuated potential at the saturated stage peaks in the ITGdominated region,and contributions from the TEM(dominating in the higher k_(θ)region)to the nonlinear transport can be neglected.In the adiabatic electron model,the zonal radial electric field is found to be mainly driven by the turbulent energy flux,and the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect.However,in the kinetic electron model,the turbulent energy flux is not strong enough to drive the zonal radial electric field in the nonlinear saturated stage.The kinetic electron effects on the mechanism of the turbulence-driven zonal radial electric field should be further investigated.

Severe Methodological Deficiencies Associated with Claims of Domestic Livestock Driving Climate Change

Reduction of global livestock numbers and meat consumption have been recommended for climate change mitigation. However, the basic assumptions made to come up with that kind of recommendations reveal severe methodological deficiencies： （1） Carbon footprint, emission intensity, and life-cycle assessments of domestic livestock products reported in scientific literature consistently overlooked the necessity of correcting non CO2 GHG （greenhouse gas） emissions （nitrous oxide and methane） from managed ecosystems for baseline emission scenarios over time and space （pristine ecosystem and/or pre-climate change emissions）; （2） Uncertainties associated with the climate sensitivity of anthropogenic GHG-emissions have been ignored; （3） Inconsistencies in the methodological treatment of land use change （deforestation） in emission intensity calculations （per unit of product） can be detected in the literature; （4） The virtual lack of a discernable livestock signal in global methane distribution and historical methane emission rates has not been acknowledged; theoretical bottom up calculations do not reflect the relative insignificance of livestock-born methane for the global methane budget; （5） Potential substrate induced enhancement of methane breakdown rates have not been taken into consideration. A tremendous over-assessment of potential livestock contribution to climate change is the logical consequence of these important methodological deficiencies which have been inexorably propagated through recent scientific literature.

Definition of Business as Usual and Its Impacts on Assessment of Mitigation Efforts

Business as Usual （BaU） scenario in developing countries has been a debated issue in climate change negotiations. This paper analyzes different definitions of BaU and points out that the major difference among these definitions is how to set the starting point of BaU projections, that is the so called base year. Some international institutions use current policy scenarios to project a BaU trajectory of developing countries. Such definition will lead to an underestimation of BaU emissions of developing countries and thus an underestimation of mitigation efforts. This paper concludes with a suggestion to use a without policy scenario with a clear base year as definition of BaU. Such a definition will set an objective benchmark to assess mitigation efforts of develonin countries.