René Garduño

Mexico's contribution to global radiative forcing by major anthropogenic greenhouse gases: CO2, CH4 and N2O

The IPCC (2013) gives simplified formulas to compute the radiative forcing (RF) resulting from the increase in anthropogenic greenhouse gases (AGG): carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O) and halocarbons. These formulas allow to compute the global RF of these gases relative to their pre-industrial (1750 A.D.) concentrations, and are used in this work to estimate the contribution of Mexico to the global RF by its emissions of CO 2 (the most significant of the AGG), CH 4 and N 2 O during the period 1990-2011, which are reported in the Inventario Nacional de Emisiones de Gases de Efecto Invernadero (National Inventory of Greenhouse Gases Emissions, INEGEI) (INECC, 2013). In comparison, by 2010 the national emissions per capita of Argentina, Spain and the United States were 108.8, 110.8 and 327.0% of the Mexican emissions, respectively, in units of equivalent CO 2 . Mexico’s CO 2 emissions retained in the atmosphere during 1990-2011 amount to 4 624 457 Gg; they are higher than those of Spain and Argentina together, and represent 1/12 of the USA contribution. Mexico’s contribution is 1.47% of the global RF due to CO 2 , with a similar proportion than Spain and Argentina, but a smaller fraction compared to that of the USA (1/15). The main uncertainties of our computations for Mexico’s contribution to the global RF come from national emissions; the INEGEI indicates that the emissions considered for the calculation of uncertainties represent 89% of the total emissions of the inventory, resulting in a total uncertainty of ±5.6%. We are aware that, as a consequence, the concentration increase of CH 4 and N 2 O due to Mexico’s emissions retained in the atmosphere during 1990-2011 is lower than their respective uncertainties for global concentrations: 1.72 vs. 2 ppbv and 0.13 vs. 1 ppbv.

Past and future climates simulated with the Adem thermodynamic model

Palaeoclimates from 18 kyr BP on and the anthropogenic climate change due to the present CO2 increase have been computed using the Adem thermodynamic model. Temperature results for 18 kyr BP are lower than at present for almost all the Northern Hemisphere, with extreme anomalies in the north of the continents. The main cause is the snow-ice cover, the insolation delays the annual cycle by about one season, and the CO2 reinforces the anomaly. From 18 to 14 kyr BP, the continental climate was colder than at present due to the extended snow-ice, then it became wanner from May to November, following the insolation pattern. Over the oceans this anomaly was smoother and delayed by about one season. For 4 kyr BP, the surface and tropospheric average annual temperatures were almost the same as at present, but the seasonal variability was larger, with winter and spring colder, and summer and autumn warmer. Over continents this effect is stronger at the surface than above, and the opposite is true over oceans. These results agree well with those from other authors. For the CO2 doubling, the temperature increases by a few degrees centigrade, and a relative drought appears in most continents.