Dark Energy at a Crossroads: Tension with expansion history of the Universe and its possible resolution

The recent measurements of the expansion history of the universe by several low-redshift observations are at large tension with similar measurement by Planck using CMB. In this talk, I shall discuss this issue and provide a possible solution to resolve this tension. I shall show that the presence of negative cosmological constant may naturally arise in resolving such tension. I shall discuss possible implications for such a cosmological scenario.