Which war in 2001 is subjectively deemed a world war?
War on Terror The War on Terror (WoT), also known as the Global War on Terrorism (GWOT), is a metaphor of war referring to the international military campaign that was launched by the U.S. government after the September 11 attacks in the U.S. in 2001.  U.S. president George W. Bush first used the term ""war on terrorism"" on 16 September 2001, and then ""war on terror"" a few days later in a formal speech to Congress. In the latter speech, George Bush stated, "Our enemy is a radical network of terrorists and every government that supports them." The term was originally used with a particular focus on countries associated with al-Qaeda. The term was immediately criticised by such people as Richard B. Myers, chairman of the Joint Chiefs of Staff, and more nuanced ones subsequently came to be used by the Bush administration to publicly define the international campaign led by the U.S.; it was never used as a formal designation of U.S. operations in internal government documentation.
Nuclear warfare Nuclear warfare (sometimes atomic warfare or thermonuclear warfare) is a military conflict or political strategy in which nuclear weaponry is used to inflict damage on the enemy. Nuclear weapons are weapons of mass destruction; in contrast to conventional warfare, nuclear warfare can produce destruction in a much shorter time-frame and can have a long-lasting radiological warfare dimension. A major nuclear exchange would have long-term effects, primarily from the fallout released, and could also lead to a "nuclear winter" that could last for decades, centuries, or even millennia after the initial attack. Some claimed that the result would be that almost every human on Earth could starve to death. Other analysts however dismiss the nuclear winter hypothesis, and calculate that even with nuclear weapon stockpiles at Cold War highs, although there would be billions of casualties, billions more rural people would nevertheless survive.