Query: The climate debate is, in reality, about a 1.6 watts per square metre or 0.5 per cent discrepancy in the poorly known planetary energy balance."

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Percentage <=SEP=> In mathematics , a percentage is a number or ratio expressed as a fraction of 100 . It is often denoted using the percent sign , '' % '' , or the abbreviations `` pct . '' , `` pct '' ; sometimes the abbreviation `` pc '' is also used . A percentage is a dimensionless number ( pure number ) .

Watts Up With That? <=SEP=> Watts Up With That ? ( or WUWT ) is a blog promoting climate change denial that was created by Anthony Watts in 2006 .   The blog predominantly discusses climate issues with a focus on anthropogenic climate change , generally accommodating beliefs that are in opposition to the scientific consensus on climate change . Contributors include Christopher Monckton and Fred Singer as guest authors . In November 2009 , the blog was one of the first websites to publish emails and documents from the Climatic Research Unit controversy , and a driving force behind its coverage .   In the early months of 2010 , it was reported the site might be `` the most read climate blog in the world , '' and in 2013 Michael E. Mann referred to it as the leading climate change denial blog .

Emissions trading <=SEP=> Emissions trading or cap and trade is a government-mandated , market-based approach to controlling pollution by providing economic incentives for achieving reductions in the emissions of pollutants . In contrast to command-and-control environmental regulations such as best available technology ( BAT ) standards and government subsidies , cap and trade ( CAT ) schemes are a type of flexible environmental regulation that allows organizations to decide how best to meet policy targets . Various countries , states and groups of companies have adopted such trading systems , notably for mitigating climate change .   A central authority ( usually a governmental body ) allocates or sells a limited number of permits to discharge specific quantities of a specific pollutant per time period . Polluters are required to hold permits in amount equal to their emissions . Polluters that want to increase their emissions must buy permits from others willing to sell them . Financial derivatives of permits can also be traded on secondary markets .   In theory , polluters who can reduce emissions most cheaply will do so , achieving the emission reduction at the lowest cost to society . Cap and trade is meant to provide the private sector with the flexibility required to reduce emissions while stimulating technological innovation and economic growth .   There are active trading programs in several air pollutants . For greenhouse gases , which cause climate change , permit units are often called carbon credits . The largest greenhouse gases trading program is the European Union Emission Trading Scheme , which trades primarily in European Union Allowances ( EUAs ) ; the Californian scheme trades in California Carbon Allowances , the New Zealand scheme in New Zealand Units and the Australian scheme in Australian Units . The United States has a national market to reduce acid rain and several regional markets in nitrogen oxides .

London <=SEP=> London -LSB- ˈlʌndən -RSB- is the capital and most populous city of England and the United Kingdom . Standing on the River Thames in the south east of the island of Great Britain , London has been a major settlement for two millennia . It was founded by the Romans , who named it Londinium . London 's ancient core , the City of London , largely retains its 1.12 sqmi medieval boundaries . Since at least the 19th century , `` London '' has also referred to the metropolis around this core , historically split between Middlesex , Essex , Surrey , Kent , and Hertfordshire , which today largely makes up Greater London , See also : Independent city § National capitals . governed by the Mayor of London and the London Assembly.The London Mayor is not to be confused with the Lord Mayor of London who heads the City of London Corporation , which administers the City of London .   London is a leading global city in the arts , commerce , education , entertainment , fashion , finance , healthcare , media , professional services , research and development , tourism , and transportation . It is crowned as the world 's largest financial centre and has the fifth - or sixth-largest metropolitan area GDP in the world.Rankings of cities by metropolitan area GDP can vary as a result of differences in the definition of the boundaries and population sizes of the areas compared , exchange rate fluctuations and the method used to calculate output . London and Paris are of broadly similar size in terms of total economic output which can result in third party sources varying as to which is the fifth-largest city GDP in the world . A report by the McKinsey Global Institute published in 2012 estimated that London had a city GDP of US$ 751.8 billion in 2010 , compared to US$ 764.2 billion for Paris , making them respectively the sixth - and fifth-largest in the world . A report by PricewaterhouseCoopers published in November 2009 estimated that London had a city GDP measured in purchasing power parity of US$ 565 billion in 2008 , compared to US$ 564 billion for Paris , making them respectively the fifth - and sixth-largest in the world . The McKinsey Global Institute study used a metropolitan area with a population of 14.9 million for London compared to 11.8 million for Paris , whilst the PricewaterhouseCoopers study used a metropolitan area with a population of 8.59 million for London compared to 9.92 million for Paris . London is a world cultural capital . It is the world 's most-visited city as measured by international arrivals and has the world 's largest city airport system measured by passenger traffic . London is the world 's leading investment destination , hosting more international retailers and ultra high-net-worth individuals than any other city . London 's universities form the largest concentration of higher education institutes in Europe . In 2012 , London became the first city to have hosted the modern Summer Olympic Games three times .   London has a diverse range of people and cultures , and more than 300 languages are spoken in the region . Its estimated mid-2015 municipal population ( corresponding to Greater London ) was 8,673,713 , the largest of any city in the European Union , and accounting for 12.5 % of the UK population . London 's urban area is the second most populous in the EU , after Paris , with 9,787,426 inhabitants at the 2011 census . The city 's metropolitan area is the most populous in the EU with 13,879,757 inhabitants , while the Greater London Authority states the population of the city-region ( covering a large part of the south east ) as 22.7 million .  London was the world 's most populous city from around 1831 to 1925 .   London contains four World Heritage Sites : the Tower of London ; Kew Gardens ; the site comprising the Palace of Westminster , Westminster Abbey , and St Margaret 's Church ; and the historic settlement of Greenwich ( in which the Royal Observatory , Greenwich marks the Prime Meridian , 0 ° longitude , and GMT ) . Other famous landmarks include Buckingham Palace , the London Eye , Piccadilly Circus , St Paul 's Cathedral , Tower Bridge , Trafalgar Square , and The Shard . London is home to numerous museums , galleries , libraries , sporting events , and other cultural institutions , including the British Museum , National Gallery , Natural History Museum , Tate Modern , British Library , and West End theatres . The London Underground is the oldest underground railway network in the world .