The planet's climate has constantly been changing over geological time. The global average temperature today is about 15C, though geological evidence suggests it has been much higher and lower in the past. However, the current period of warming is occurring more rapidly than many past events. Scientists are concerned that the natural fluctuation, or variability, is being overtaken by a rapid human-induced warming that has serious implications for the stability of the planet's climate.
Greenhouse effect refers to the way the Earth's atmosphere traps some of the energy from the Sun. Solar energy radiating back out to space from the Earth's surface is absorbed by atmospheric greenhouse gases and re-emitted in all directions. The energy that radiates back down to the planet heats both the lower atmosphere and the surface. Without this effect, the Earth would be about 30C colder, making our planet hostile to life. The effects of a changing climate can also be seen in vegetation and land animals. These include earlier flowering and fruiting times for plants and changes in the territories (or ranges) occupied by animals.
Since the industrial revolution began in 1750, CO2 levels have risen by more than 30% and methane levels have risen more than 140%. The concentration of CO2 in the atmosphere is now higher than at any time in at least 800,000 years. Satellite data shows an average increase in global sea levels of some 3mm per year in recent decades. A large proportion of the change in sea level is accounted for by the thermal expansion of seawater. As seawater warms up, the molecules become less densely packed, causing an increase in the volume of the ocean. But the melting of mountain glaciers and the retreat of polar ice sheets are also important contributors. Most glaciers in temperate regions of the world and along the Antarctic Peninsula are in retreat.
Climate change is expected to increase the frequency of extreme weather events - though linking any single event to global warming is complicated. Scientists forecast more rainfall overall, but say the risk of drought in inland areas during hot summers will increase. More flooding is expected from storms and rising sea levels. There are, however, likely to be very strong regional variations in these patterns. Poorer countries, which are least equipped to deal with rapid change, could suffer the most.
Plant and animal extinctions are predicted as habitats change faster than species can adapt, and the World Health Organization (WHO) has warned that the health of millions could be threatened by increases in malaria, water-borne disease and malnutrition. As an increased amount of CO2 is released into the atmosphere, there is increased uptake of CO2 by the oceans, and this leads to them becoming more acidic. This ongoing process of acidification could pose major problems for the world's coral reefs.
The UN has endorsed a goal of limiting global warming to no more than 2C over pre-industrial levels by the end of the century. But more than 100 poorer countries and low-lying, small-island states are calling for a tougher goal of 1.5C. Developing nations say industrialized countries should do more to cut emissions, having polluted for much longer. But rich countries insist that the burden must be shared to reach the 2C target. One of the few firm decisions from the 2009 UN climate conference in Copenhagen was a pledge from rich economies to provide $100 billion (93 billion Euros) a year in financial support for poor countries from 2020 to develop technology and build infrastructure to cut emissions. Where that money will come from and how it will be distributed has yet to be agreed.
UN climate conference, known as COP21, organized by world powers to find credible solutions for fast tempos of climate change, is scheduled for 30 Nov - 11 Dec 2015 in Paris where a terror attack has caused havoc and it appeared world leaders would be forced to focus on terror instead of climate challenge.
World leaders opened pivotal climate talks in Paris, saying the stakes are too high to end the talks without achieving a binding agreement to help slow the pace of global climate change. "A political moment like this may not come again," U.N. Secretary-General Ban Ki-moon told leaders gathered for the conference. "We have never faced such a test. But neither have we encountered such great opportunity."
The talks opened with a moment of silence for victims of the November 13 terror attacks in Paris, and the tragedy served as a touchstone for world leaders who opened the conference with addresses urging action. "What greater rejection of those who would tear down our world than marshaling our best efforts to save it," President Barack Obama said in his speech. French President Francois Hollande noted that "never have the stakes been so high because this is about the future of the planet, the future of life." "And yet two weeks ago, here in Paris itself, a group of fanatics was sowing the seeds of death in the streets," he said.
COP 21 - the 21st session of the Conference of the Parties - will see more than 190 nations gather in Paris to discuss a possible new global agreement on climate change, aimed at reducing greenhouse gas emissions to avoid the threat of dangerous warming due to human activities. Leaders of 150 nations, along with 40,000 delegates from 195 countries, are attending the conference, called COP21. COP stands for Conference of Parties, an annual forum to try to tackle climate change on a global political level. The leaders have one mission: Agree on legally binding reductions in greenhouse gas emissions meant to hold global average temperatures short of a 2 degrees Celsius increase over preindustrial global temperatures.
The ultimate aim is to limit warming to 2C (3.6F) above pre-industrial levels, widely seen as a dangerous threshold. Since 1880, the average global temperature has already risen by almost 1C. About 0.6C of this has occurred in the past three decades.
Paris conference tries to hammer out a deal to tackle global warming. Scientists believe we are adding to the natural greenhouse effect with gases released from industry and agriculture (known as emissions), trapping more energy and increasing the temperature. This is commonly referred to as global warming or climate change. The most important of these greenhouse gases in terms of its contribution to warming is water vapour, but concentrations show little change and it persists in the atmosphere for only a few days. Most man-made emissions of CO2 are through the burning of fossil fuels, as well as through cutting down carbon-absorbing forests. Other greenhouse gases such as methane and nitrous oxide are also released through human activities, but their overall abundance is small compared with carbon dioxide.
U.S. President Obama says the current generation is 'the last that can do something' about climate change. Negotiations for climate deal began on November 29 afternoon but the main talks start from the next day. US President Obama says the current generation is 'the last that can do something' about climate change. $20bn annual funding for clean energy projects to be announced, starting in 2020, from public and private sources. About 150 world leaders are due to attend the Paris talks including US President Barack Obama, China's Xi Jinping, Russia's Vladimir Putin, Pakistani premier Nawaz Sharif and India's Narendra Modi .
On November 30, the leaders of the main players necessary to achieve the ambitious climate goal -- China and the United States -- sat down together at the COP21. They are the largest producers of greenhouse gases. Obama told the conference that the United States recognizes its role in creating climate change and its role in solving the issue. But he said the agreement should be global in nature, assertive and flexible. He also addressed economic issues associated with climate change, saying recent economic growth in the United States has come despite a lack of growth in carbon emissions, proving that climate advancements need not come at the expense of the economy or individual livelihoods. "That's what we seek in these next two weeks -- not simply an agreement to roll back the pollution we put into the skies, but an agreement that helps us lift people from poverty without condemning the next generation to a planet that is beyond its capacity to repair," he said. He also said developed countries must help island nations and others that have contributed little to climate change but are the first to be feeling its effects.
Chinese President Xi Jinping said that the conference "is not a finish line, but a new starting point" and that any agreement must take into account the differences among nations. "Countries should be allowed to seek their own solutions, according to their national interest," he said.
US President Barack Obama has said the UN climate conference in Paris could be a "turning point" in global efforts to limit future temperature rises. President Obama urged negotiators to deliver a meaningful deal, because the "next generation is watching". He added that recent years had shown that the global economy had grown while emissions had remained flat, breaking the old arguments for inaction "that economic growth and environmental protection were in conflict".
Russian President Vladimir Putin also addressed the conference. During negotiations for the preceding Kyoto Protocol, Russia was the last industrialized nation to ratify the global agreement, allowing the landmark deal to come into force in 2001.
Echoing President Obama, Putin said: "We have demonstrated we can ensure economic development and take care of our environment at the same time." In a diplomatic play on semantics, probably to highlight the differing points of view between industrialized and emerging economies, Chinese President Xi Jinping told the conference he did not see the Paris talks as a turning point nor a "finish line, but a new starting point". He said that climate change went beyond national borders and that it was "a shared mission for all mankind", before reiterating China's pledge to start cutting its emissions from a peak in 2030.
Hundreds of thousands of people have marched worldwide to demand action to stop climate change, the day before a UN summit starts in Paris. One campaign group says more than 570,000 protesters took part in marches on all the main continents. Activists want action at the Paris talks to limit the rise in the average global temperature to 2C (3.6F) above pre-industrial levels. In Paris itself, more than 200 demonstrators were arrested after clashes. The climate changes affect us all and it is here, through mobilization, that we show how united our countries are against those larger nations that continue to pollute and refuse to cut back.
Elsewhere across the world: an estimated 50,000 people took part in a march in central London, where opposition leader Jeremy Corbyn addressed crowds. some of the earliest protests in the day took place in the Marshall Islands, a US territory in the Pacific Ocean threatened by rising seas. in Kenya, a march took place across the equator/ a small group took part in a march across a glacier in the south of Chile; the mayor of Sydney in Australia tweeted to say that there were "at least 45,000" demonstrators, making it the biggest ever such march in the city.
Earlier, a human chain was formed by hundreds linking arms in the French capital along the route of a march that was called off after the 13 November attacks that killed 130 people. A gap in the chain was left in front of the Bataclan concert hall, where 89 people were killed. Hundreds of pairs of shoes were left on Place de la Republique to remember those left frustrated in their plans to march. Among them were a pair donated by Pope Francis, who has called for urgent action on climate change.
Some of the demonstrators in Place de la Republique in Paris were apparently protesting against France's state of emergency, and have been disowned by the main organizers. The order, banning public gatherings, was put into place after the 13 November attacks. Many of those involved in the clashes wore masks or covered their faces. Candles from a makeshift memorial in the square were thrown at police. Interior Minister Bernard Cazeneuve said 208 people had been arrested, of whom 174 are still in custody.
Meanwhile, the leaders of 10 of the world's biggest oil companies have offered their qualified support for a new global treaty on climate change. The producers of 20% of the world's oil and gas say they share the ambition to limit warming to 2C. They promise to work to reduce the greenhouse gas intensity of the global energy mix. But green groups were dismissive, saying that "arsonists don't make good firefighters".
The Oil and Gas Climate Initiative represents major producers including BP, Shell, Saudi Aramco and Total among others.
Given flexibility of world leaders in dealing with climate change and the very nature of climate change process it is not an easy task to suggest future of global climate.
However, announcements like this by world leaders will increase the sense of optimism. However, goodwill alone won't secure a deal as divisions among the parties about the form, costs and content of an agreement run deep. Negotiator countries will try to reach a deal within two weeks aimed at reducing global carbon emissions and limiting global warming to 2C (3.6F).
Much of the discussion in Paris is expected to centre on an agreement to limit global warming to 2C (3.6F). However, assessments of the more than 180 national climate action plans submitted by countries to the summit suggest that if they are implemented, the world will see a rise of nearer to 3C. When the Earth warms about 2C above pre-industrial times, scientists say there will be dangerous and unpredictable impacts on our climate system.
Let us all wait for the concluding communiqué of the Paris COP21.