butterflies of southern species such as Papilio memnon Linnaeus (Figure 1-7). Also in recent years, deer habitats have been expanding into mountain areas, causing serious damage to agricultural and forestry businesses. Deer are compelled to migrate in order to avoid heavy snows at the onset of winter, and the said trend of changing deer habitats is considered to correlate with increasing warm areas and global warming.

### 2. Projections of Global Warming

According to the IPCC AR4 WG1 report, best estimates and likely ranges for global average surface air warming for six SRES emissions marker scenarios are given in this assessment and are shown in figure 1-8. For example, the best estimate for the low scenario (B1) is $ 1.8^{\circ} $ C (likely range is $ 1.1^{\circ} $ C to $ 2.9^{\circ} $ C), and the best estimate for the high scenario (A1FI) is $ 4.0^{\circ} $ C (likely range is $ 2.4^{\circ} $ C to $ 6.4^{\circ} $ C).

The IPCC AR4 WG2 report suggests that approximately 20-30% of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5°C

Globally, the potential for food production is projected to increase with increases in local average temperature over a range of 1-3°C, but above this it is projected to decrease.

Increases in sea surface temperature of about 1-3°C are projected to result in more frequent coral bleaching events and widespread mortality. With higher temperatures, hundreds of million people are projected to be exposed to water stress.

Over the course of this century, net carbon uptake by terrestrial ecosystems is likely to peak before mid-century and then weaken or even reverse, thus amplifying climate change (See paragraph 5, Section 3 of Chapter 2).

Thus, increases in global mean temperature of less than 1-3°C above 1990 levels, some impacts are projected to produce benefits in some places and some sectors, and produce costs in other places and other sectors. It is very likely that all regions will experience either declines in net benefits or increases in net costs for increases in temperature greater than about 2-3°C.

If the human society continues to emit GHG at the current pace, the said increase level could be exceeded. It can be said that “global warming doomsday clock” is ticking. In order for us to stop this clock from striking catastrophe, it is urgently required to accelerate our efforts to fight against global warming.

### 3. Mechanism of Global Warming and Necessity of Immediate Actions

Figure 1-8: Projections of the IPCC Special Report on (SRES)

Note: The Emission Scenarios of the IPCC Special Report on Emission Scenarios (SRES)

A1. The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil-intensive (A1FI), non-fossil energy sources (A1T) or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies).

A2. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.

B1. The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource-efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

B2. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

An illustrative scenario was chosen for each of the six scenario groups A1B, A1FI, A1T, A2, B1 and B2. All should be considered equally sound.

The SRES scenarios do not include additional climate initiatives, which means that no scenarios are included that explicitly assume implementation of the United Nations Framework Convention on Climate Change or the emissions targets of the Kyoto Protocol.

Source: IPCC AR4 WG1 report

The Earth’s temperature depends mainly on the balance of incoming solar energy and outgoing terrestrial radiation.

The Earth is heated by solar light. Then, the Earth radiates infrared, which is absorbed by atmospheric greenhouse gases including carbon dioxide, and the heat is returned to the Earth’s surface (re-radiation). Through this process, the Earth’s surface temperature is maintained at an average of about $ 14^{\circ} $ C, providing an optimal condition for living creatures.

However, since the Industrial Revolution, the human society has come to consume a large amount of fossil fuels by combusting them, resulting in enormous GHG emissions such as carbon dioxide into the air. This led to the hike in GHG concentrations in the