Brasil Pack Trends 2020

BrasilPackTrends2020 176 sustainabi l ity & ethics FIGURE 7.1 Observed changes Source: IPCC, 2007 reports (INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, 2012). Its most recent report to date, the AR-4 (IPCC, 2007) is based on 29,000 series of data corresponding to 75 studies, each one with at least 20 years of observation. According to the 4th IPCC report, the warming of the climate system is unequivocal, evidenced by observations of increased global average air and ocean temperatures and by melting glaciers and rising global average level of the oceans, as shown in Figure 7.1. The rise in sea level is consistent with global warming. The sea level increased at an average rate of 1.8 mm per year between 1961 and 2003, and at an average rate of 3.1mm per year between 1993 and 2003. The thermal expansion of the oceans has contributed to the increase of sea levels, along with the reduction of the glaciers and ice caps. The reductions observed in the areas covered by snow and ice are also consistent with the warming. The satellite data, since 1978, show that annual average area of the sea arctic ice has been reduced by 2.7% per decade, with more intense reductions in the summer, of 7.4% per decade. The glacial mountains and the mean snow covers have decreased at both hemispheres. Temperatures at the top of the permafrost layer have generally increased since the 1980s in the Arctic by up to 3°C. Observed changes in (a) global average surface temperature; (b) global average sea level from tide gauge (blue) and satellite (red) data; and (c) Northern Hemisphere snow cover for March-April. All differences are relative to corresponding averages for the period 1961-1990. Smoothed curves represent decadal averaged values while circles show yearly values. The shaded areas are the uncertainty intervals estimated from a comprehensive analysis of known uncertainties (a and b) and from the time series (c).