Although 150 nations signed the kyoto protocol, which aims to reduce greenhouse gas emissions,
question options:
the treaty does not go into effect until 2025.
the european union has since rejected the treaty.
the united states failed to ratify this treaty.
polar ice caps have ceased receding, casting doubt on climate change.

the United States failed to ratify this treaty.

Explanation:

When the protocol was first signed in 1997, president Bill Clinton signed alongside all the other leaders. But Congress didn't ratify it and then in 2001, President George Bush Jr rejected the treaty altogether. Bush claimed that the protocol was inefficient, but did not take any alternative measures.

The protocol went into effect in 2004, but evidence shows it has been unable to curb the emission of CO2.

In 2013 there was another attempt, but this time neither Russia nor the US ratified it.