Generate an appropriate single-sentence summary for the given text such that it includes the main topic of the text.

How does it work? There have been attempts to allow richer countries to cut their emissions by paying for the development of carbon lowering schemes in poorer nations. However, the effectiveness of these schemes has been questioned, with research indicating that some have created more emissions than they have actually curtailed. Of greater significance have been the so called cap and trade schemes, at regional, national and international levels. They work by setting an overall limit or cap on the amount of emissions that are allowed from significant sources of carbon, including the power industry, automotive and air travel. Governments then issue permits up to the agreed limit, and these are either given free or auctioned to companies in the sector. If a company curbs its own carbon significantly it can trade the excess permits on the carbon market for cash. If it's not able to limit its emissions it may have to buy extra permits. Schemes are up and running in the European Union and in several regions of the United States, but attempts at a national scheme in the US foundered in the Senate in 2010. What are the advantages? Cap and trade schemes have been very effective in tackling environmental problems in the past, with trading in sulphur dioxide permits helping to limit acid rain in the US. The big attraction for governments concerned with stemming CO2 is that carbon trading is much easier to implement than expensive direct regulations, and unpopular carbon taxes. If regional cap and trade schemes can be joined up globally, with a strong carbon price, it could be a relatively pain-free and speedy method to help the world decarbonise. And the disadvantages? Creating a market in something with no intrinsic value such as carbon dioxide is very difficult. You need to promote scarcity - and you have to strictly limit the right to emit so that it can be traded. In the world's biggest carbon trading scheme, the EU ETS, political interference has created gluts of permits. These have often been given away for free, which has led to a collapse in the price and no effective reductions in emissions. Another problem is that offset permits, gained from paying for pollution reductions in poorer countries, are allowed to be traded as well. The importance of these permits in reducing carbon emissions is questionable and the effectiveness of the overall cap and trade scheme is also reduced. What are the alternatives? There are two basic options. Carbon taxes and direct regulations. Taxes on energy content or production are in place in many European countries. Taxes exist in India, Japan and South Korea and they have been imposed then repealed in Australia. Other governments have tried to regulate their way to lower emissions. This approach is being tried in the US, where President Obama has imposed a Clean Power Plan on energy producers, designed to reduce emissions from this sector by 32% by 2030.
Carbon trading is a market-based system aimed at reducing greenhouse gases that contribute to global warming, particularly carbon dioxide emitted by burning fossil fuels.

The world's fourth-largest smartphone maker raised $4.7bn (£3.5bn) - just over half the target it had hoped for - valuing the company at $54bn. As the first of many Chinese tech firms to list in Hong Kong in 2018, it marks a disappointing start for the sector. Chinese stocks have fallen recently in the lead up to the US-China trade war. Xiaomi's trading debut was the biggest technology share sale since fellow China tech giant Alibaba raised $25bn in 2014. It was also being seen as an important tech listing for Chinese peers scheduled to make their own initial public offerings in the coming months. They include online food delivery and ticketing platform Meituan Dianping and entertainment giant Tencent Music, which both plan to list their shares on the Hong Kong stock exchange later this year. But shares in Xiaomi, the firm often called China's Apple, fell from HK$17 to as low as HK$16 in the first hour of trade, although the price recovered to close at HK$16.80. Global ambitions Outside its home market in China, Xiaomi is a major player in India where it rivals Samsung as the most the popular handset maker. Last year, Xiaomi moved into the Spanish market and reports suggest it is also looking to get into the US to take on Apple. While smartphones make up 70% of Xiaomi's revenue, its fastest-growing division focuses on internet-connected home appliances and gadgets, including air purifiers and rice cookers. Despite sales of 114.62bn yuan (£13.2bn; $18bn) in 2017, the firm reported a net loss of 43.9bn yuan compared with a net profit of 491.6bn yuan in 2016. Xiaomi also faces stiff competition from the likes of Apple, Huawei, Lenovo and Samsung, as well as local mobile phone makers Vivo and Oppo. Its Hong Kong share listing comes as Chinese stock markets have been on the defensive amid growing trade tensions between the US and China. On Friday, the US fired the opening shot in an outright trade war between the two economic giants. Against that backdrop, Hong Kong's benchmark Hang Seng index fell 2.7% last week and is down 5.8% so far this year. The trade tensions have also affected confidence among investors in mainland China, with the Shanghai Composite also down sharply this year.
Shares in Chinese smartphone maker Xiaomi suffered a lacklustre first day of trading in Hong Kong, dropping 6% at first before recovering some ground.

Prime minister Mahinda Rajapakse and the leader of the opposition Ranil Wickramasinghe have already been selected as presidential candidates by the two main political parites. Both are yet to announce their policies. What should be the main issues of the election? Have your say. Mr. Rajapakse is a popular leader. But mere popularity is not enough to solve the issues faced by the country. He is yet to spell out his policies on key issues. Further, entering into an alliance with JVP is bound to keep him tied down when it comes to making key decisions. Sri Lanka needs fixed policies on key areas (i.e education, economy,foreign policy,security etc.)which do not change with a change in government. What we lack the most is decipline at all levels of the society. This should be fixed first.Mohamed Halim, Manama, Bahrain I think Of the two, Mr.Wickramasinghe has better vision for the country. On the other hand, the PM has not clearly mentioned his stance on one of the key issues - the ethnic issue. Mr.Rajapakse's approach seem to be of getting everybody's support by not providing a clear policy. I personally hope & pray that the people of this country will not tolorate ambiguity when selecting apresident. If so we will continue to be the same.Prasanan, Colombo, Sri Lanka Our beautiful country can be saved only by a leader who is capable of making decisions on his own, and not a one who is greedy for power like a unfaithful greedy dog goes behind other people for aid to win the election (because he or she cannot do it by their self), this itself shows the lack of confidence of the leader and lack of trust our people have for him. Our country cannot be saved as long as racists such as JVP and Jathika Hela Urumaya are allowed to operate and corrupt the minds of our people and ruin our country.Nihal, Kandy, Sri Lanka The election of Mahinda or Ranil to govern the country is like asking Murali to face Brett Lee & Magrath in the first 15 overs instead of Sanath. Both will miserably fail in the onslaught from LTTE as both of them does not have the hunger in the belly for the good of the country. Ranil is such a puppet that I could control him with my TV remote.Suresh Mirando, Sydney, Australia What Sri Lanka need is a strong leader who understand the difference between ethnic issue faced by minorities and the terrorist issue perpetuated by the LTTE and its leader Prabaharan. As long as the future president is unable to clearly distinguish between the two and project this reality to the world hopes for a prosperous sri Lanka remains grim.Tharindra Ranasinghe, Houston, USA Mahinda has done nothing to the country as a Senior Minister for 10 yrs and as PM for 1 1/2 yrs.He has no vision, no policy, Now all of a sudden he wants to talk directly to Prabakaran. What was he doing for the last 11 yrs? Ranil has a vision, his policies are clear. A good decision maker.Ahamed Hussain, Kuala Lumpur, Malaysia The P-TOMS, CFA, and peace process should be considered on top of the list. There are so many Tsunami victims in the North & East are still waiting for the foreign aid. Both Sinhala presidential candidates should put aside their politics and try to help those in need. It has been already 8-months and neither politicians seems to care about those minorities. Mahinda Rajapakse's close ties with JVP is not promissing for those want to see peace in Sri Lanka. JVP already wants to scrap P-TOMS and CFA.Siva Nathan, Toronto, Canada It's better to choose a known devil than an unknown angel. Hopefully Mahinda might become President in case if the JVP support him irrespective of his claim that he will be talking to H.E. Pirabakaran to end the conflict. Or else Ranil might lead but none of them will get the 51% of the vote to become EXECUTIVE President.Abdul Rahuman, Colombo, Sri Lanka The policy should be based on the resolving the terrorist problem in the north and development of the country as a whole. It was clear there were less development during past few decades owing to the war in north and east. There should be a settlement with dignity for the peace loving people of Sri Lanka and not the facist LTTE. LTTE cannot build north and east because of their autocratic and facist ideology. There should be an economic development based on self reliance and we can follow the Indian and Chinese trading systems.This is the final chance to Sri Lankns to select whether to stand up as a nation and defeat LTTE terrorists.Shanthan Welayuthan, Wembley, United Kingdom Both leaders are curupted and neither of them have clear vision to get the whole nation out of the trouble.both fellows are making their own strategies to be crowned as president.the ethnic issue is a political football for opportunistic politicians.it is very unlikely that either Ranil or Mahinda would address burning problems of the people, rather they would be playing around with peaple's votes near election time and enjoy themself when the elections are faraway.Sugath Senevirathne, Hounslow, UK Right now, only one visionary leader in Sri Lanka is Mr. Prabaharan. Tamils don't want to waste their time, sharing the country and resources with Sinhalese as they [Sinhalese] are only good at destroying the country, not building it. Let Tamils go their own way and Sinhalese fight themselves.Prem Sivasamy, London, UK The economy is in the first place.Rest of the problums will automaticaly go away with the economic growth.Jagath, Colombo, Sri Lanka Will the UNP actually field Ranil for the Presidency against Mahinda? I won't believe this until Nomination Papers are handed over. Ranil has absolutely no chance in a Presidential Race against Mahinda Rajapakse. Mahinda will win by a massive margin.Aruna Wickramatunga, Colombo, Sri Lanka The country needs a strong leader with a vision. SL still got hope we shouldn't give up! (1)Let's hope for a leader who can settle the war. I do not call this an Ethnic problem since we Sri Lanknans be it Tamil, Sinhalese or Muslims lived and will be living cohesively. It just a misunderstanding that has grown. I guess direct talks with parties in concern (may be two leaders) could settle the differences.(both parties will have to forget & forgive and start fresh. After all we are fiting with another set of Srilankans and not bunch of invaders. 2) Let's hope for a Leader who will have a vision to build the economy Both canditates got potential, yet who comes out with clear statements on these two should be given preference.Namal Abhayawickrama, Indonesia I think Hon. Ranil will be more experienced Than Prime Minister Rajapakse. People gave a mandate for Hon. Ranil for five years which was unfairly taken back by the Sandanya Regime. Therefore he deserve and should be given a chance a president. Also the fact that Prime Minister will have a pact with JVP the chances of negotiated settlement with LTTE will become remote.Navrooze Rawoof, Colombo, Sri Lanka Speaking as a Tamil born and bred in the UK, and as a son of a Tamil Doctor forced to move to England due to the transparent preferential treatment of the Sinhalese at the time, I would say that the ethnic struggle has been the biggest cause of contention in SL for the last 50 years. The ethnic struggles that have made the largest progress in recent history have always had the least corrupt, most forthright leaders at their hub, people like Gandhi, JFK and Mandela to name but a few. I'd see Ranil Wickramasinghe as the best of a bad bunch as I feel it is time for a change, the current presidents favourite (Rajapakse) will undoubtedly be as untransparent and single-minded as Chandrika herself and will therefore not present much hope for the future of a country that has such greatness in its potential.Sean Jehan, London, UK If one of them becom the president and the other one stay as PM,would be great. I mean for the future of the country. We need a uncorrupted National government.Rizmy Mueen, Opfikon, Switzerland Ranil's stand on the ethnic issue is crystal clear.His economic reforms are also solid. On the other hand the Prime Minister has been unable to put forward a coherent set of proposals to solve the ethnic problem.He also lacks contemporary economic reforms.Suranjith Fernando, Edinburgh, UK The stand on the ethnic problem, the economy, the law and order situation including violations by party MPs and their children.Dhammika W, Colombo, Sri Lanka Both of them are not strong leaders and they will not resolve countrys ethnic problem. It is impossible to build a strong economy without resolving this issue. It will be like one step forward and two step backward.Shan Mylvagaman, London, UK It is very ridiculous that, there is one main issue to be addressed on this ellection!every thing has became a very major issue in sri lanka now but the biggest issue is , most of us not seen those . every body talking about only the ethnic crisis... which only one of thousands...! the issues are not valid with SL politicians , that will not do what they say....simply say ... sri lanka needs just a leader who can lead us .. and i dont see anyboy in SL now or another 20 years time .. but till we get " THE PRINCE OF DIYASEN" atleast we should have a someboy to keep the mother land unsell... for that definitely RANIL is not the man.Indika Shirantha, Shanghai, China

The election commissioner is expected to announce the date of this year's presidential elections.

