Which year did ISO revise the environmental management standard to 14001:2015?

The environmental management standard ISO 14001 was indeed revised in 2015. This revision introduced several important changes to enhance its effectiveness in promoting a sustainable approach to environmental management. The 2015 version emphasizes the need for organizations to integrate environmental management into their overall business strategies more thoroughly, focusing on leadership, context, and stakeholder engagement.

In contrast, the years 2004, 2010, and 2020 do not correspond to the major revisions of this standard. The earlier 2004 update focused on clarifications and improvements to the existing framework rather than a substantial overhaul. The 2010 timeframe does not relate to any updates as the last significant change before 2015 was indeed the 2004 version. The year 2020 is also not relevant since there have been no updates to the standard in that year.

Therefore, the accurate answer is 2015, marking a significant milestone in ISO 14001's evolution towards a more strategic approach to environmental management.