Carbon dioxide (CO₂) is the most significant greenhouse gas produced by human activities, primarily from burning fossil fuels, and is the main contributor to climate change.

The United States signed the CTBT in 1996 but has not ratified it. Ratification requires Senate approval, which has not been granted.

The Human Development Index (HDI) measures a country's average achievements in health, education, and income, reflecting the overall well-being and standard of living of its people.

SAARC (South Asian Association for Regional Cooperation) includes Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka. Myanmar is not a member.

NATO headquarters are located in Brussels, Belgium, not in any of the cities listed.

Andorra does not maintain a regular army. Its defense is the responsibility of France and Spain, and its small volunteer force is only ceremonial.

Dr. Martin Luther King, Jr. is renowned for leading the American civil rights movement through non-violent civil disobedience, advocating for equality and justice in the United States.

November 25th is designated as the International Day for the Elimination of Violence Against Women by the United Nations. The date was chosen to honor the Mirabal sisters, political activists assassinated in the Dominican Republic in 1960.

The United Nations' International Day of Peace is celebrated on 21 September each year. It recognizes efforts to end conflict and promote peace worldwide, and is marked by calls for ceasefire and non-violence.

The International Day for the Elimination of Racial Discrimination is observed every year on 21 March. This date commemorates the Sharpeville massacre in South Africa in 1960, when police killed 69 people at a peaceful protest against apartheid. The United Nations General Assembly proclaimed the day in 1966, urging the international community to intensify efforts to eliminate all forms of racial discrimination.