Effect of the Kyoto Protocol on Sea-Level Change

As part of an international effort to mitigate the potential human-induced climate change, the so-called Annex I countries agreed to reduce their emissions of carbon dioxide and other greenhouse gases at the Third Conference of the Parties to the United Nations Framework Convention on Climate Change held at Kyoto, Japan in December, 1997. The terms of this Protocol call for industrialized nations to reduce their emissions of six greenhouse gases below 1990 levels by 5.2% on average by 2008-2012. In particular, the United States agreed to a 7% reduction, while the European Union agreed to an 8% reduction, and Japan a 6% reduction. If the Protocol is ratified, these nations will be committed to legally-binding restrictions.

  

Figure 9: Changes in sea level calculated for the reference scenario (dashed line) and for a scenario implementing the Kyoto protocol (full line) for Greenland (left), Antarctica (middle) and net sea-level change (right). Units are cm.

The impact of the Kyoto Protocol on changes in sea-level is calculated here in Fig. 9 by contrasting the results derived from a simulation in which no restrictions are imposed on the emissions of greenhouse gases which are allowed to grow unconstrained (note that because of assumptions about emission rates of greenhouse gases, this scenario has slight differences from the REF run used in the previous section) and a simulation in which the terms of the Kyoto protocol are implemented and emissions by the industrialized nations are held constant after the 2008-2012 compliance period (Reilly et al. (1999)). The global mean warming is reduced to 2^oC when the Kyoto Protocol is imposed, from 2.4^oC in the unconstrained case. The difference is however twice as large in polar regions where the Protocol reduces the warming from 4.6^oC to 3.8^oC by 2100. The protocol reduces the increase in sea-level due to increased melting on the Greenland ice sheet by $\sim$ 1 cm, it however also reduces the decrease in sea-level linked to increasing accumulation over Antarctica by little more than the same amount. The Kyoto protocol thus leaves the prediction of sea-level change due to modifications in the mass balance of the ice sheets virtually unchanged at -3 cm by the end of the 21^st century. This effect is however only one of numerous contributions to sea-level rise, the contributions from thermal expansion, the melting of small glaciers and ice caps and changes in surface and ground water uses are not included in this estimate.