how much could sea level rise in the 21st century
Future sea level The Intergovernmental Panel on Climate Change (2007)[1] projected sea level would reach 0.18 to 0.59 m above present by the end of the 21st century but lacked an estimate of ice flow dynamics calving.[2][3] Calving was added by Pfeffer et al. (2008)[4] indicating 0.8 to 2 m of SLR by 2100 (favouring the low end of this range). Rahmstorf (2007)[5] estimated SLR will reach 0.5 to 1.4 m by the end of the century. Pielke (2008)[6] points out that observed SLR has exceeded the best case projections thus far. These approximations and others indicate that global mean SLR may reach 1 m by the end of this century. However, sea level is highly variable and planners considering local impacts must take this variability into account.
World population Population size fluctuates at differing rates in differing regions. Nonetheless, population growth is the long-standing trend on all inhabited continents, as well as in most individual states. During the 20th century, the global population saw its greatest increase in known history, rising from about 1.6 billion in 1900 to over 6 billion in 2000. A number of factors contributed to this increase, including the lessening of the mortality rate in many countries by improved sanitation and medical advances, and a massive increase in agricultural productivity attributed to the Green Revolution.[104][105][106]