Global warming: What if we do nothing

If mankind fails to curtail global warming, we will have to deal with fallout ranging from massive refugee crises and submerged cities to scorching heatwaves and drought, scientists say. Here is what could happen if they come up empty-handed:

Hotter Temperatures Without additional action, Earth is on track to heat up by about 4°C by the end of the century, compared to pre-industrial levels.

“Business as usual” emissions scenario would “lead to a very high risk of severe, widespread and irreversible” impacts, according to the UN intergovernmental panel on climate change (IPCC).

Rising seas By 2100, the world's oceans would rise 26-82 centimetres over levels seen between 1986-2005, the IPCC found in its most recent assessment, which includes data up to 2012. Driving the rise are ice sheets in Greenland and Antarctica shedding mass faster than ever, melting glaciers, and oceans that expand as they warm.

Even a 2 C rise as targeted by the UN would submerge land currently occupied by 280 million people, according to Climate Central, a US-based research group.

Extreme weather Superstorms, bone-chilling cold snaps and intense heat waves could become more common — and more extreme — due to global warming. While the link between specific weather events an-d climate remains hard to nail down, recent research has teased out climate cha-nge as an aggravating factor for deadly floods, snowstorms, typhoons and heat waves. Not all nasty hurricanes or heat waves, however, can be chalked up to climate change, scientists caution.

Water dilemma Global warming can lead to long-running droughts and devastating floods, which means some parts of the world will not have enough water and others too much. Heavy rains carry the risk of flooding that can send people fleeing for their lives, destroy homes and crops.

Humanitarian crises Global warming can spur disease, ravage crops and push more people into poverty. Conflict over water or smaller harvests could instigate war or mass migration. People living on low-lying islands could become climate refugees.