Significant changes in physical and biological systems are occurring on all continents and in most oceans, with a concentration of available data in Europe and North America. Most of these changes are in the direction expected with warming temperature. Here we show that these changes in natural systems since at least 1970 are occurring in regions of observed temperature increases, and that these temperature increases at continental scales cannot be explained by natural climate variations alone. Given the conclusions from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report that most of the observed increase in global average temperatures since the mid-twentieth century is very likely to be due to the observed increase in anthropogenic greenhouse gas concentrations, and furthermore that it is likely that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica, we conclude that anthropogenic climate change is having a significant impact on physical and biological systems globally and in some continents.

a b s t r a c tWe present density functional theory (DFT) calculations for CO hydrogenation on different transition metal surfaces. Based on the calculations, trends are established over the different monometallic surfaces, and scaling relations of adsorbates and transition states that link their energies to only two descriptors, the carbon oxygen binding energies, are constructed. A micro-kinetic model of CO hydrogenation is developed and a volcano-shaped relation based on the two descriptors is obtained for methanol synthesis. A large number of bimetallic alloys with respect to the two descriptors are screened, and CuNi alloys of different surface composition are identified as potential candidates. These alloys, proposed by the theoretical predictions, are prepared using an incipient wetness impregnation method and tested in a highpressure fixed-bed reactor at 100 bar and 250-300°C. The activity based on surface area of the active material is comparable to that of the industrially used Cu/ZnO/Al 2 O 3 catalyst. We employ a range of characterization tools such as inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis, in situ X-ray diffraction (XRD) and in situ transmission electron microscope (TEM) to identify the structure of the catalysts.

Trends in surface temperature over the last 100, 50, and 30 yr at individual grid boxes in a 5° latitude–longitude grid are compared with model estimates of the natural internal variability of these trends and with the model response to increasing greenhouse gases and sulfate aerosols. Three different climate models are used to provide estimates of the internal variability of trends, one of which appears to overestimate the observed variability of surface temperature at interannual and 5-yr time scales. Significant warming trends are found at a large fraction of the individual grid boxes over the globe, a much larger fraction than can be explained by internal climate variations. The observed warming trends over the last 50 and 30 yr are consistent with the modeled response to increasing greenhouse gases and sulfate aerosols in most of the models. However, in some regions, the observed century-scale trends are significantly larger than the modeled response to increasing greenhouse gases and sulfate aerosols in the atmosphere. Warming trends consistent with the response to anthropogenic forcing are detected at scales on the order of 500 km in many regions of the globe.

Anthropogenic forcings have contributed to global and regional warming in the last few decades and likely affected terrestrial precipitation. Here we examine changes in major Köppen climate classes from gridded observed data and their uncertainties due to internal climate variability using control simulations from Coupled Model Intercomparison Project 5 (CMIP5). About 5.7% of the global total land area has shifted toward warmer and drier climate types from 1950–2010, and significant changes include expansion of arid and high-latitude continental climate zones, shrinkage in polar and midlatitude continental climates, poleward shifts in temperate, continental and polar climates, and increasing average elevation of tropical and polar climates. Using CMIP5 multi-model averaged historical simulations forced by observed anthropogenic and natural, or natural only, forcing components, we find that these changes of climate types since 1950 cannot be explained as natural variations but are driven by anthropogenic factors.

A lagged maximum covariance analysis is applied to investigate linear covariability between monthly sea ice concentration (SIC) and atmosphere circulation in the Northern Hemisphere. The dominant signal is the atmospheric forcing of SIC anomalies throughout the year, but a wintertime atmospheric signal resembling the negatively polarized Arctic Oscillation/North Atlantic Oscillation is significantly correlated with persistently reduced SIC anomalies in the North Atlantic and Pacific sides of Arctic Shelf seas up to the preceding summer. The leading time of SIC anomalies provides an implication for skillful predictability of wintertime atmospheric variability.