Virtually, one usually experiences a significant coolness around and under trees in comparison to open sunshine, with qualitative variations. This study was conducted to investigate the effect of irrigation with saline water (8000 and 16000 ppm) on some trees and their effect on transpiration rates, and the impact of these trees on reducing the atmospheric temperature and therefore their impact on climate change. The trees under study were used in the study: Bauhinia variegata, Cassia fistula, Cassia nodosa, Eucalyptus camaldulensis, Ficus retusa and Khaya senegalensis. In general, results indicated that, the atmosphere was cooler around Cassia fistula by reduction of atmospheric temperature by 6.5 °C (also, it produces odorous flowers) followed by Eucalyptus camaldulensis (5.3 °C). Reduction of temperature was correlated with high transpiration rate after irrigation with saline water after 2, 4 and 8 days of irrigation. It can be concluded that, using of saline water in irrigation of ornamental trees is efficient to induce the cooling effect in our gardens. Also, results showed the superiority of some trees in their efficiency in absorbing CO₂ and were in the following order: Ficus religiosa (87.65); Bauhinia variegata (83.76); Cassia nodosa (81.53); Eucalyptus camaldulensis (80.15); Khaya senegalensis (79.04); Chorisia speciosa (73.29); Cassia fistula (72.54); Bombax malabaricum (72.34); Erythrina variegata (71.82); Ficus retusa (71.33); Ficus benghalensis (67.20) and Tipuana speciosa (65.99).