Device for providing a warning about an absence of belaying for a climber equipped with a harness, the device comprising: - a link intended to be attached to the harness; - an enclosure intended to be fixed to the harness; - a pressure sensor, arranged in the enclosure to measure a barometric pressure; - detection means comprising an inclination sensor, the inclination sensor comprising a housing positioned fixedly on the link, the detection means being configured to detect a movement of the link within a range of positive inclinations when the link extends in a plane above a horizontal reference plane (P ref), the positive inclinations in the range being the dihedral angles formed between the plane in which the link extends and the horizontal reference plane (P ref); the positive inclinations in the range that are detected by the inclination sensor containing a final positive inclination corresponding to the dihedral angle formed between the plane in which the link extends when the link is held by a belaying system and the horizontal reference plane (P ref), the detection means being configured such that the positive inclinations in the range that are detected by the inclination sensor form a solid angle extending above the horizontal reference plane (P ref), and about a vertical axis that is the normal to the horizontal reference plane (P ref); the detection means being configured to output a detection signal comprising: a first state, indicating that the link is in the range of positive inclinations, a second state, indicating that the link is outside the range of positive inclinations; - a microprocessor, arranged in the enclosure, connected to the pressure sensor and to the detection means, and configured to: compute a variation in the barometric pressure measured by the pressure sensor, send a warning signal if and only if the variation in the barometric pressure exceeds a predetermined threshold and the detection signal is in the second state. - a link intended to be attached to the harness; - an enclosure intended to be fixed to the harness; - a pressure sensor, arranged in the enclosure to measure a barometric pressure; - detection means comprising an inclination sensor, the inclination sensor comprising a housing positioned fixedly on the link, the detection means being configured to detect a movement of the link within a range of positive inclinations when the link extends in a plane above a horizontal reference plane (P ref), the positive inclinations in the range being the dihedral angles formed between the plane in which the link extends and the horizontal reference plane (P ref); the positive inclinations in the range that are detected by the inclination sensor containing a final positive inclination corresponding to the dihedral angle formed between the plane in which the link extends when the link is held by a belaying system and the horizontal reference plane (P ref), the detection means being configured such that the positive inclinations in the range that are detected by the inclination sensor form a solid angle extending above the horizontal reference plane (P ref), and about a vertical axis that is the normal to the horizontal reference plane (P ref); the detection means being configured to output a detection signal comprising: a first state, indicating that the link is in the range of positive inclinations, a second state, indicating that the link is outside the range of positive inclinations; a first state, indicating that the link is in the range of positive inclinations, a second state, indicating that the link is outside the range of positive inclinations; - a microprocessor, arranged in the enclosure, connected to the pressure sensor and to the detection means, and configured to: compute a variation in the barometric pressure measured by the pressure sensor, send a warning signal if and only if the variation in the barometric pressure exceeds a predetermined threshold and the detection signal is in the second state. compute a variation in the barometric pressure measured by the pressure sensor, send a warning signal if and only if the variation in the barometric pressure exceeds a predetermined threshold and the detection signal is in the second state.