Khi bạn lần đầu tiên nhìn vào biến đổi khí hậu, bạn nhận ra ít bạn biết. Bạn nhìn vào nó, bạn càng nhận ra ít ai biết như thế nào. Thủy ngân từ Trung Quốc, bụi từ châu Phi, khói từ Mexico - tất cả đều là tự do trôi qua biên giới Mỹ và gây ô nhiễm không khí của hàng triệu người Mỹ thở . USA Today, 14 tháng 3 năm 2005 Trong thời cổ đại, Trái đất có thời kỳ khi nồng độ CO2 tối đa là ppm (trong giai đoạn Than). Nhưng cuộc sống vẫn. | 8 Global Concerns When you first look into climate change you realize how little you know. The more you look into it the more you realize how little anyone knows. Dr. Ralph Cicerone UC Irvine March 1992 Mercury from China dust from Africa smog from Mexico all of it drifts freely across . borders and contaminates the air millions of Americans breathe . USA Today March 14 2005 In ancient times the Earth had periods when maximum CO2 concentrations were 6 000 ppm in the Carboniferous period . But life still goes on. There is no proven link between human activity and global warming. Yury Izrael IPCC vice president June 2005 The earth and its atmosphere are a dynamic system of which human activities form only a small part. Meteorology and long-range transport of pollutants geogenic versus biogenic versus anthropogenic emission sources air pollution control strategies ocean temperatures volcanoes and sunspots as well as their second order effects make for a system too complex to truly understand. In no other area of air quality management is there greater uncertainty than in some aspects of global issues. Other issues such as intercontinental pollution transport and stratospheric ozone impacts are clearer because observation and measurement methods have improved with time and there is a longer record of such measurements. However proven facts are still few and opinions are many regarding human air pollutant impacts on issues such as climate and acid rain. Popular concerns for intercontinental pollution transport deal with chronic health effects and fairness issues stratospheric ozone concerns are for potential surface UV light penetration and fears of cancer climate change concerns include the potential for rising sea levels or impacts on agriculture acid rain issues include possible effects on vegetation and food supplies. In each case we know some things well such as temperatures and gas concentrations at various points and times. In other cases the best we have are
