Final answer:
The critical concentration to avoid the worst impacts of global warming, suggested to be 350 ppm of CO₂, has been exceeded with current levels at around 400 ppm; this highlights the urgency for action.
Step-by-step explanation:
The critical concentration of CO₂ that scientists believe will avoid the worst consequences of global warming is a much-debated topic. Current scientific wisdom suggests that 350 parts per million (ppm) of CO₂ is the threshold above which it is not considered 'safe' for our planet's climate and ecosystems. We have surpassed this level, with current atmospheric concentration of CO₂ at approximately 400 ppm and increasing. This indicates that we are already in a dire situation, as climate change effects such as disrupted ecosystems, melting ice sheets, and rising sea levels are becoming more apparent. Furthermore, historical data show a pattern of atmospheric CO₂ cycling between 180 and 300 ppm, numbers much lower than today's levels. It is crucial for mitigation and adaptation strategies, including conservation efforts and reducing emissions, to address this urgent situation.