In my opinion there's some truth to this, but I'm not sure the people who wish this would happen have the power to make it happen. Exposure makes it harder for them, and, as with any plot affecting large numbers of people, there are sometimes unintended consequences as well.
In a nutshell, the elites are planning to (or wish they could) kill up to 90% of the world's population (or sterilize them) in order to "save the earth", presumably for themselves and their families. This conspiracy theory also encompasses other conspiracies, such as chemtrails, mind control, HAARP, fluoride, GMO, vaccine overuse/contamination, nanobots, old Nazis imported here, and the looming police state.
Here are source documents only. I will add more as I find them. A lot of this is rather dry reading. They couch their intent behind a lot of jargon. The general rule of thumb is, the more jargonistic, jingoistic, and confusing it sounds, the more attention you should pay to it, like a contract lawyer, because there be the dragons.
Weather as a Weapon
http://www.thetruthdenied.com/news/wp-content/uploads/2012/10/vol3ch15.pdf "Owning the Weather", military research that was prepared for the USAF.
http://www.geoengineeringwatch.org/documents-2/ Here is a link to a lot of geoengineering documents, going back to as early as 1966. Included in this collection is another link to a copy of Agenda 21.
Hunger as a Weapon
http://wlym.com/text/NSSM200.htm Henry Kissinger's now-declassified 1974 report recommending the creation of famines in order to depopulate other countries as a strategic measure.
Death by Greenie Weenie Land Grabs: Agenda 21
http://www.thetruthdenied.com/news/wp-content/uploads/2012/11/Agenda21.pdf Here's another link to a copy of the Agenda 21 document from the 1992 Rio conference where it started. Touted as "sustainable development", Agenda 21 is being used to steal land via zoning changes and environmental restrictions, ruin the economies of downtown areas and mom-and-pop businesses via weaponized parking and street plans, and deposit large numbers of the nonworking poor into every well-off neighborhood via forced integration schemes.
Food, health and supplement control
The Codex Alimentarius is a collection of food standards established by a UN group called the Codex Alimentarius Commission, which is under the WHO and the FAO. In trade disputes under the WTO, if one country has adopted Codex and the other hasn't, the one that has wins the dispute. So even though the Codex claims to be a collection of suggestions, it's de facto coercive.
In 1996, the German delegation of the Codex Alimentarius Commission tried to get all supplements classified as drugs, and that no herb, vitamin or mineral should be sold for preventive or therapeutic reasons. But protests prevented them from getting their way. People who like supplements and herbal medicine don't like Codex, for this reason. Also, some traditional foods of various countries are banned under Codex, and it allows pesticides that are banned in the US. If the US adhered to Codex, we would be required to re-allow those pesticides.
http://www.codexalimentarius.net/web/index_en.jsp Codex Alimentarius official website
http://www.archive.org/stream/CodexAlimentariusCommission/CodexAlimentariusCommission_djvu.txt Codex Alimentarius' 2008 meeting, full text.
Death By Police State
http://www.gpo.gov/fdsys/pkg/BILLS-112s1867es/pdf/BILLS-112s1867es.pdf Text of the 2012 NDAA as passed by the US Senate. This law allows for indefinite detention of American citizens apprehended on US soil, on mere suspicion of "terrorism". The specific charges can be kept secret by the US. So basically, you can be put away for a long period of time based on some intelligence or security official's whim, your relatives will not be told where you are or what the charges are against you, and your lawyer won't even be allowed to see any of the purported evidence.
Here is the 2014 NDAA. It continues the obliteration of habeas corpus started some years back.
Just in case you think you'll be safe from this if you're not engaged in terrorism, may I point out that many of the people detained at Guantanamo Bay are innocent. They are just people who were arrested at the same time as some terrorists, people who were staying at the same hotel, for example. But they can't get out. Source documents that prove this are published by Wikileaks, here http://wikileaks.ch/gitmo.
Surveillance Gone Amok
This is a torrent of Wikileaks' Spy Files, a compilation of documents relating to the international spying "industry", that they released in Dec. 2013.
All this spying is not new. This link has a lot of links to Project Echelon source documents.Project Echelon was a way that countries in the "free world" could get around laws forbidding them to spy on their own citizens by having another friendly country do it for them and then swap data. This had gone on for years before the NSA started the warrantless direct wiretapping of US citizens with their alteration of the Thinthread program.