How would scientists know that there is life existing outside of earth? what do they use?

This problem has been solved! see the answerbuilding a sea wall to prevent ocean water from encroaching on a city is an example of climate change [ select ] ["sequestration", "mitigation", "vulnerability", "adaptation"] .creating a carbon tax to provide incentives to reduce co2 emissions is an example of climate change [ select ] ["sequestration", "mitigation", "vulnerability", "adaptation"] .planting more forests is an example of enhancing carbon [ select ] ["sequestration", "mitigation", "vulnerability", "adaptation"] .the tendency to be adversely affected or lack of ability to adapt defines climate change [ select ] ["sequestration", "mitigation", "vulnerability", "adaptation"] .sequestration, adaption, mitigation, vulnerability